73 files changed, 253 insertions, 254 deletions

diff --git a/INSTALL b/INSTALL
index 119b4d4dd1d..ade9bcbf463 100644
--- a/INSTALL
+++ b/INSTALL
@@ -5,7 +5,7 @@ See the end of the file for license conditions.
 
 
 This file contains general information on building GNU Emacs.
-For more information specific to the MS-Windows, GNUstep/Mac OS X, and
+For more information specific to the MS-Windows, GNUstep/macOS, and
 MS-DOS ports, also read the files nt/INSTALL, nextstep/INSTALL, and
 msdos/INSTALL.  For information about building from a repository checkout
 (rather than a release), also read the file INSTALL.REPO.
@@ -208,7 +208,7 @@ corresponding command is 'yum-builddep emacs'.
 
 DETAILED BUILDING AND INSTALLATION:
 
-(This is for a Unix or Unix-like system.  For GNUstep and Mac OS X,
+(This is for a Unix or Unix-like system.  For GNUstep and macOS,
 see nextstep/INSTALL.  For non-ancient versions of MS Windows, see
 the file nt/INSTALL.  For MS-DOS and MS Windows 3.X, see msdos/INSTALL.)
 
diff --git a/Makefile.in b/Makefile.in
index b3f7edb2eaa..9600c1199ab 100644
--- a/Makefile.in
+++ b/Makefile.in
@@ -113,7 +113,7 @@ am__v_at_1 =
 
 # ==================== Where To Install Things ====================
 
-# Location to install Emacs.app under GNUstep / Mac OS X.
+# Location to install Emacs.app under GNUstep / macOS.
 # Later values may use these.
 ns_appbindir=@ns_appbindir@
 ns_appresdir=@ns_appresdir@
diff --git a/README b/README
index 35a31dbd31e..d227ec59cc7 100644
--- a/README
+++ b/README
@@ -86,9 +86,8 @@ There are several subdirectories:
                 in Emacs Lisp manual.
 'msdos'     holds configuration files for compiling Emacs under MS-DOS.
 'nextstep'  holds instructions and some other files for compiling the
-            Nextstep port of Emacs, for GNUstep and Mac OS X Cocoa.
-'nt'        holds various command files and documentation files that pertain
-            to building and running Emacs on Windows 9X/ME/NT/2000/XP.
+            Nextstep port of Emacs, for GNUstep and macOS Cocoa.
+'nt'        holds code and documentation for building Emacs on MS-Windows.
 'test'      holds tests for various aspects of Emacs's functionality.
 
    Building Emacs on non-Posix platforms requires tools that aren't part
diff --git a/admin/CPP-DEFINES b/admin/CPP-DEFINES
index 796b57db3d8..cf8360316c2 100644
--- a/admin/CPP-DEFINES
+++ b/admin/CPP-DEFINES
@@ -22,7 +22,7 @@ WINDOWSNT	Compiling the native MS-Windows (W32) port.
 __MINGW32__     Compiling the W32 port with the MinGW or MinGW-w64 ports of GCC.
 _MSC_VER        Compiling the W32 port with the Microsoft C compiler.
 MINGW_W64       Compiling the W32 port with the MinGW-w64 port of GCC.
-DARWIN_OS       Compiling on Mac OS X or pure Darwin (and using s/darwin.h).
+DARWIN_OS       Compiling on macOS or pure Darwin (and using s/darwin.h).
 SOLARIS2
 USG
 USG5_4
@@ -30,7 +30,7 @@ USG5_4
 ** Distinguishing GUIs **
 
 HAVE_NTGUI      Use the native W32 GUI for windows, frames, menus&scrollbars.
-HAVE_NS         Use the NeXT/OpenStep/Cocoa UI under Mac OS X or GNUstep.
+HAVE_NS         Use the NeXT/OpenStep/Cocoa UI under macOS or GNUstep.
 NS_IMPL_GNUSTEP Compile support for GNUstep implementation of NS GUI API.
 NS_IMPL_COCOA   Compile support for Cocoa (Apple) implementation of NS GUI API.
 HAVE_X11        Compile support for the X11 GUI.
diff --git a/configure.ac b/configure.ac
index 19b44bd34ce..9f12a2b7331 100644
--- a/configure.ac
+++ b/configure.ac
@@ -342,8 +342,8 @@ OPTION_DEFAULT_ON([toolkit-scroll-bars],[don't use Motif or Xaw3d scroll bars])
 OPTION_DEFAULT_ON([xaw3d],[don't use Xaw3d])
 OPTION_DEFAULT_ON([xim],[don't use X11 XIM])
 AC_ARG_WITH([ns],[AS_HELP_STRING([--with-ns],
-[use Nextstep (OS X Cocoa or GNUstep) windowing system.
-On by default on Mac OS X.])],[],[with_ns=maybe])
+[use Nextstep (macOS Cocoa or GNUstep) windowing system.
+On by default on macOS.])],[],[with_ns=maybe])
 OPTION_DEFAULT_OFF([w32], [use native MS Windows GUI in a Cygwin build])
 
 OPTION_DEFAULT_ON([gpm],[don't use -lgpm for mouse support on a GNU/Linux console])
@@ -599,7 +599,7 @@ case "${canonical}" in
     opsys=openbsd
   ;;
 
-  ## Apple Darwin / Mac OS X
+  ## Apple Darwin / macOS
   *-apple-darwin* )
     case "${canonical}" in
       *-apple-darwin[0-9].*) unported=yes ;;
@@ -1864,14 +1864,14 @@ Either fix this, or re-configure with the option '--without-ns'.])])
 
   macfont_file=""
   if test "${NS_IMPL_COCOA}" = "yes"; then
-    AC_MSG_CHECKING([for OSX 10.6 or newer])
+    AC_MSG_CHECKING([for Mac OS X 10.6 or newer])
     AC_COMPILE_IFELSE([AC_LANG_PROGRAM([#include <AppKit/AppKit.h>],
                                      [
 #ifdef MAC_OS_X_VERSION_MAX_ALLOWED
 #if MAC_OS_X_VERSION_MAX_ALLOWED >= 1060
  ; /* OK */
 #else
- error "OSX 10.6 or newer required";
+ error "Mac OS X 10.6 or newer required";
 #endif
 #endif
                     ])],
@@ -1880,7 +1880,7 @@ Either fix this, or re-configure with the option '--without-ns'.])])
     AC_MSG_RESULT([$ns_osx_have_106])
 
     if test $ns_osx_have_106 = no; then
-       AC_MSG_ERROR([OSX 10.6 or newer is required]);
+       AC_MSG_ERROR([Mac OS X 10.6 or newer is required]);
     fi
   fi
 fi
@@ -3562,9 +3562,9 @@ AC_CHECK_HEADERS_ONCE(malloc/malloc.h)
 GNUSTEP_CFLAGS=
 ### Use NeXTstep API to implement GUI.
 if test "${HAVE_NS}" = "yes"; then
-  AC_DEFINE(HAVE_NS, 1, [Define to 1 if you are using the NeXTstep API, either GNUstep or Cocoa on Mac OS X.])
+  AC_DEFINE(HAVE_NS, 1, [Define to 1 if you are using the NeXTstep API, either GNUstep or Cocoa on macOS.])
   if test "${NS_IMPL_COCOA}" = "yes"; then
-    AC_DEFINE(NS_IMPL_COCOA, 1, [Define to 1 if you are using NS windowing under MacOS X.])
+    AC_DEFINE(NS_IMPL_COCOA, 1, [Define to 1 if you are using NS windowing under macOS.])
   fi
   if test "${NS_IMPL_GNUSTEP}" = "yes"; then
     AC_DEFINE(NS_IMPL_GNUSTEP, 1, [Define to 1 if you are using NS windowing under GNUstep.])
@@ -4725,9 +4725,9 @@ case $opsys in
     ;;
 
   darwin)
-    dnl Not __APPLE__, as this may not be defined on non-OSX Darwin.
+    dnl Not __APPLE__, as this may not be defined on non-macOS Darwin.
     dnl Not DARWIN, because Panther and lower CoreFoundation.h use DARWIN to
-    dnl distinguish OS X from pure Darwin.
+    dnl distinguish macOS from pure Darwin.
     AC_DEFINE(DARWIN_OS, [], [Define if the system is Darwin.])
     ;;
 
diff --git a/doc/emacs/cmdargs.texi b/doc/emacs/cmdargs.texi
index f0f686f855c..881bf11a9f0 100644
--- a/doc/emacs/cmdargs.texi
+++ b/doc/emacs/cmdargs.texi
@@ -550,11 +550,11 @@ variables is not set, the category defaults to the value of the
 @env{LANG} is not set.  But if @env{LC_ALL} is specified, it overrides
 the settings of all the other locale environment variables.
 
-On MS-Windows and OS X, if @env{LANG} is not already set in the
+On MS-Windows and macOS, if @env{LANG} is not already set in the
 environment, Emacs sets it based on the system-wide default.  You can
 set this in the ``Regional Settings'' Control Panel on some versions
 of MS-Windows, and in the ``Language and Region'' System Preference on
-OS X.
+macOS.
 
 The value of the @env{LC_CTYPE} category is
 matched against entries in @code{locale-language-names},
diff --git a/doc/emacs/macos.texi b/doc/emacs/macos.texi
index b0597dc2499..6e6520b60bc 100644
--- a/doc/emacs/macos.texi
+++ b/doc/emacs/macos.texi
@@ -3,19 +3,19 @@
 @c See file emacs.texi for copying conditions.
 @node Mac OS / GNUstep
 @appendix Emacs and Mac OS / GNUstep
-@cindex Mac OS X
+@cindex macOS
 @cindex Macintosh
 @cindex GNUstep
 
   This section describes the peculiarities of using Emacs built with
 the GNUstep libraries on GNU/Linux or other operating systems, or on
-Mac OS X with native window system support.  On Mac OS X, Emacs can be
+macOS with native window system support.  On macOS, Emacs can be
 built either without window system support, with X11, or with the
 Cocoa interface; this section only applies to the Cocoa build.  This
-does not support versions of Mac OS X earlier than 10.6.
+does not support versions before Mac OS X 10.6.
 
   For various historical and technical reasons, Emacs uses the term
-@samp{Nextstep} internally, instead of ``Cocoa'' or ``Mac OS X''; for
+@samp{Nextstep} internally, instead of ``Cocoa'' or ``macOS''; for
 instance, most of the commands and variables described in this section
 begin with @samp{ns-}, which is short for @samp{Nextstep}.  NeXTstep
 was an application interface released by NeXT Inc during the 1980s, of
@@ -84,7 +84,7 @@ set, which often causes the subprocesses it launches to behave differently than
 they would when launched from the shell.
 
 For the PATH and MANPATH variables, a system-wide method
-of setting PATH is recommended on Mac OS X, using the
+of setting PATH is recommended on macOS, using the
 @file{/etc/paths} files and the @file{/etc/paths.d} directory.
 
 @node Mac / GNUstep Customization
@@ -117,8 +117,8 @@ close the altered one.
 Useful in this context is the listing of all faces obtained by
 @kbd{M-x list-faces-display}.
 
-@cindex Core Text, on Mac OS X
-In Mac OS X, Emacs uses a Core Text based font backend
+@cindex Core Text, on macOS
+In macOS, Emacs uses a Core Text based font backend
 by default.  If you prefer the older font style, enter the following
 at the command-line before starting Emacs:
 
diff --git a/doc/emacs/msdos.texi b/doc/emacs/msdos.texi
index 6ad12d646a1..47ba23b95aa 100644
--- a/doc/emacs/msdos.texi
+++ b/doc/emacs/msdos.texi
@@ -366,7 +366,7 @@ Emulate @sc{gnu} systems; this is the default.  This sets
 Emulate Unix systems.  Like @code{GNU}, but sets
 @code{ls-lisp-verbosity} to @code{(links uid)}.
 @item MacOS
-Emulate MacOS@.  Sets @code{ls-lisp-ignore-case} to @code{t}, and
+Emulate macOS@.  Sets @code{ls-lisp-ignore-case} to @code{t}, and
 @code{ls-lisp-dirs-first} and @code{ls-lisp-verbosity} to @code{nil}.
 @item MS-Windows
 Emulate MS-Windows.  Sets @code{ls-lisp-ignore-case} and
diff --git a/doc/emacs/mule.texi b/doc/emacs/mule.texi
index e735343cc75..882d75f5e61 100644
--- a/doc/emacs/mule.texi
+++ b/doc/emacs/mule.texi
@@ -745,7 +745,7 @@ exactly what to do for end-of-line conversion:
 @item @dots{}-unix
 Don't do any end-of-line conversion; assume the file uses
 newline to separate lines.  (This is the convention normally used
-on Unix and GNU systems, and Mac OS X.)
+on Unix and GNU systems, and macOS.)
 
 @item @dots{}-dos
 Assume the file uses carriage-return linefeed to separate lines, and do
@@ -757,8 +757,8 @@ Emacs doesn't support directly.})
 
 @item @dots{}-mac
 Assume the file uses carriage-return to separate lines, and do the
-appropriate conversion.  (This was the convention used on the
-Macintosh system prior to OS X.)
+appropriate conversion.  (This was the convention used in Classic Mac
+OS.)
 @end table
 
   These variant coding systems are omitted from the
@@ -1393,7 +1393,7 @@ of @code{standard-fontset-spec}.  This fontset's name is
 @noindent
 or just @samp{fontset-standard} for short.
 
-  On GNUstep and Mac OS X, the standard fontset is created using the value of
+  On GNUstep and macOS, the standard fontset is created using the value of
 @code{ns-standard-fontset-spec}, and on MS Windows it is
 created using the value of @code{w32-standard-fontset-spec}.
 
diff --git a/doc/lispref/display.texi b/doc/lispref/display.texi
index f94628ce105..a49bfc8ca8c 100644
--- a/doc/lispref/display.texi
+++ b/doc/lispref/display.texi
@@ -6958,7 +6958,7 @@ Emacs is displaying the frame using X.
 Emacs is displaying the frame using native MS-Windows GUI.
 @item ns
 Emacs is displaying the frame using the Nextstep interface (used on
-GNUstep and Mac OS X).
+GNUstep and macOS).
 @item pc
 Emacs is displaying the frame using MS-DOS direct screen writes.
 @item nil
diff --git a/doc/lispref/nonascii.texi b/doc/lispref/nonascii.texi
index 9cf3b5750f2..e4581b3d68e 100644
--- a/doc/lispref/nonascii.texi
+++ b/doc/lispref/nonascii.texi
@@ -1034,8 +1034,7 @@ Unix convention, used on GNU and Unix systems, is to use the linefeed
 character (also called newline).  The DOS convention, used on
 MS-Windows and MS-DOS systems, is to use a carriage-return and a
 linefeed at the end of a line.  The Mac convention is to use just
-carriage-return.  (This was the convention used on the Macintosh
-system prior to OS X.)
+carriage-return.  (This was the convention used in Classic Mac OS.)
 
 @cindex base coding system
 @cindex variant coding system
diff --git a/doc/lispref/os.texi b/doc/lispref/os.texi
index 0d999ae9b99..6b9b2c7faf3 100644
--- a/doc/lispref/os.texi
+++ b/doc/lispref/os.texi
@@ -888,7 +888,7 @@ Berkeley BSD and its variants.
 Cygwin, a Posix layer on top of MS-Windows.
 
 @item darwin
-Darwin (Mac OS X).
+Darwin (macOS).
 
 @item gnu
 The GNU system (using the GNU kernel, which consists of the HURD and Mach).
diff --git a/doc/misc/efaq.texi b/doc/misc/efaq.texi
index 72a90a1ff21..9efe0e73c5c 100644
--- a/doc/misc/efaq.texi
+++ b/doc/misc/efaq.texi
@@ -1206,7 +1206,7 @@ Emacs can be started as a daemon in the background.
 
 @cindex NeXTstep port
 @cindex GNUstep port
-@cindex Mac OS X Cocoa
+@cindex macOS Cocoa
 @item
 There is a new NeXTstep port of Emacs.  This supports GNUstep and Mac OS
 X (via the Cocoa libraries).  The Carbon port of Emacs, which supported
@@ -3341,7 +3341,7 @@ problem (@pxref{Reporting bugs}).
 * Emacs for MS-DOS::
 * Emacs for MS-Windows::
 * Emacs for GNUstep::
-* Emacs for Mac OS X::
+* Emacs for macOS::
 @end menu
 
 @node Finding Emacs on the Internet
@@ -3561,13 +3561,13 @@ For MS-DOS, @pxref{Emacs for MS-DOS}.
 Beginning with version 23.1, Emacs supports GNUstep natively.
 See the file @file{nextstep/INSTALL} in the distribution.
 
-@node Emacs for Mac OS X
-@section Where can I get Emacs for Mac OS X?
+@node Emacs for macOS
+@section Where can I get Emacs for macOS?
 @cindex Apple computers, Emacs for
 @cindex Macintosh, Emacs for
-@cindex Mac OS X, Emacs for
+@cindex macOS, Emacs for
 
-Beginning with version 22.1, Emacs supports Mac OS X natively.
+Beginning with version 22.1, Emacs supports macOS natively.
 See the file @file{nextstep/INSTALL} in the distribution.
 
 @c ------------------------------------------------------------
diff --git a/doc/misc/gnus.texi b/doc/misc/gnus.texi
index 08067b0c735..11f9f35227d 100644
--- a/doc/misc/gnus.texi
+++ b/doc/misc/gnus.texi
@@ -21520,7 +21520,7 @@ bound to mairix searches and are automatically updated.
 Mairix is a tool for indexing and searching words in locally stored
 mail.  It was written by Richard Curnow and is licensed under the
 GPL@.  Mairix comes with most popular GNU/Linux distributions, but it also
-runs under Windows (with cygwin), Mac OS X and Solaris.  The homepage can
+runs under Windows (with cygwin), macOS and Solaris.  The homepage can
 be found at
 @uref{http://www.rpcurnow.force9.co.uk/mairix/index.html}
 
diff --git a/doc/misc/idlwave.texi b/doc/misc/idlwave.texi
index 26c81d65948..32b33641656 100644
--- a/doc/misc/idlwave.texi
+++ b/doc/misc/idlwave.texi
@@ -75,7 +75,7 @@ Interactive Data Language (IDL), and running IDL as an inferior shell.
 * Sources of Routine Info::     How does IDLWAVE know about routine XYZ
 * HTML Help Browser Tips::
 * Configuration Examples::      The user is king
-* Windows and MacOS::           What still works, and how
+* Windows and macOS::           What still works, and how
 * Troubleshooting::             When good computers turn bad
 * GNU Free Documentation License:: The license for this documentation.
 * Index::                       Fast access
@@ -2372,7 +2372,7 @@ Normal hook.  Executed when @file{idlwave.el} is loaded.
 @cindex Subprocess of Emacs, IDL
 @cindex Comint, Emacs package
 @cindex Windows
-@cindex MacOS
+@cindex macOS
 
 The IDLWAVE shell is an Emacs major mode which permits running the IDL
 program as an inferior process of Emacs, and works closely with the
@@ -2382,7 +2382,7 @@ debug these programs.  The IDLWAVE shell is built on @file{comint}, an
 Emacs packages which handles the communication with the IDL program.
 Unfortunately, IDL for Windows does not have command-prompt versions and
 thus do not allow the interaction with Emacs, so the IDLWAVE shell
-currently only works under Unix and MacOSX.
+currently works under only Unix and macOS.
 
 @menu
 * Starting the Shell::          How to launch IDL as a subprocess
@@ -3533,14 +3533,14 @@ to locate library catalogs.
 @end defopt
 
 @defopt idlwave-library-path
-IDL library path for Windows and MacOS@.  Under Unix/MacOSX, will be
+IDL library path for Windows and macOS@.  Under Unix/macOS, will be
 obtained from the Shell when run.
 @end defopt
 
 @defopt idlwave-system-directory
-The IDL system directory for Windows and MacOS@.  Also needed for
+The IDL system directory for Windows and macOS@.  Also needed for
 locating HTML help and the IDL Assistant for IDL v6.2 and later.  Under
-Unix/MacOSX, will be obtained from the Shell and recorded, if run.
+Unix/macOS, will be obtained from the Shell and recorded, if run.
 @end defopt
 
 @defopt idlwave-config-directory (@file{~/.emacs.d/idlwave})
@@ -3626,7 +3626,7 @@ performance is a problem and/or the catalogs are not needed.
 @cindex User catalog
 @cindex IDL library routine info
 @cindex Windows
-@cindex MacOS
+@cindex macOS
 @cindex IDL variable @code{!DIR}
 @cindex @code{!DIR}, IDL variable
 
@@ -3651,7 +3651,7 @@ catalog must be rescanned to update it.  Creating the user catalog is
 also much slower than scanning library catalogs.
 
 You can scan any of the directories on the currently known path.  Under
-Windows and MacOS (not OSX), you need to specify the IDL search path in
+Windows, you need to specify the IDL search path in
 the variable @code{idlwave-library-path}, and the location of the IDL
 directory (the value of the @code{!DIR} system variable) in the variable
 @code{idlwave-system-directory}, like this@footnote{The initial @samp{+}
@@ -3742,10 +3742,9 @@ files.  Therefore, such local files should not be installed inside the
 many other reasons.
 
 @cindex Windows
-@cindex MacOS
 @cindex IDL variable @code{!DIR}
 @cindex @code{!DIR}, IDL variable
-Users of Windows and MacOS (not X) also must set the variable
+Users of Windows also must set the variable
 @code{idlwave-system-directory} to the value of the @code{!DIR} system
 variable in IDL@.  IDLWAVE appends @file{lib} to the value of this
 variable and assumes that all files found on that path are system
@@ -3822,7 +3821,7 @@ etc.).
 @noindent Individual platform recommendations:
 
 @itemize @bullet
-@item Unix/MacOSX: The @uref{http://www.w3m.org,@code{w3m}} browser
+@item Unix/macOS: The @uref{http://www.w3m.org,@code{w3m}} browser
 and its associated
 @uref{http://emacs-w3m.namazu.org/,@code{emacs-w3m}} emacs mode
 provide in-buffer browsing with image display, and excellent speed and
@@ -4020,18 +4019,17 @@ user is King!
 @html
 <A NAME="WINDOWS_MAC"></A>
 @end html
-@node Windows and MacOS
-@appendix Windows and MacOS
+@node Windows and macOS
+@appendix Windows and macOS
 @cindex Windows
-@cindex MacOS
-@cindex MacOSX
+@cindex macOS
 
 IDLWAVE was developed on a UNIX system.  However, thanks to the
 portability of Emacs, much of IDLWAVE does also work under different
-operating systems like Windows (with NTEmacs or NTXEmacs) or MacOS.
+operating systems like Windows (with NTEmacs or NTXEmacs).
 
 The only real problem is that there is no command-line version of IDL
-for Windows or MacOS(<=9) with which IDLWAVE can interact.  As a
+for Windows with which IDLWAVE can interact.  As a
 result, the IDLWAVE Shell does not work and you have to rely on IDLDE
 to run and debug your programs.  However, editing IDL source files
 with Emacs/IDLWAVE works with all bells and whistles, including
@@ -4112,10 +4110,10 @@ ensure @samp{idl} is on your @samp{$PATH}, or specify the full
 pathname to the idl program with the variable
 @code{idlwave-shell-explicit-file-name}.  Note that you may need to
 set your shell search path in two places when running Emacs as an Aqua
-application with MacOSX; see the next topic.
+application with macOS; see the next topic.
 
 @item @strong{IDLWAVE is disregarding my @samp{IDL_PATH} which I set
-under MacOSX}
+under macOS}
 
 If you run Emacs directly as an Aqua application, rather than from the
 console shell, the environment is set not from your usual shell
diff --git a/doc/misc/mairix-el.texi b/doc/misc/mairix-el.texi
index 8deead52dc6..69d3fc42277 100644
--- a/doc/misc/mairix-el.texi
+++ b/doc/misc/mairix-el.texi
@@ -68,7 +68,7 @@ database.
 Mairix is a tool for indexing and searching words in locally stored
 mail.  It was written by Richard Curnow and is licensed under the
 GPL@.  Mairix comes with most popular GNU/Linux distributions, but it also
-runs under Windows (with cygwin), Mac OS X and Solaris.  The homepage can
+runs under Windows (with cygwin), macOS and Solaris.  The homepage can
 be found at
 @uref{http://www.rpcurnow.force9.co.uk/mairix/index.html}
 
diff --git a/doc/misc/org.texi b/doc/misc/org.texi
index a5239acb59f..a6f9dbde7cb 100644
--- a/doc/misc/org.texi
+++ b/doc/misc/org.texi
@@ -6616,7 +6616,7 @@ applying it to another one.
 @vindex org-clock-idle-time
 By customizing the variable @code{org-clock-idle-time} to some integer, such
 as 10 or 15, Emacs can alert you when you get back to your computer after
-being idle for that many minutes@footnote{On computers using Mac OS X,
+being idle for that many minutes@footnote{On computers using macOS,
 idleness is based on actual user idleness, not just Emacs' idle time.  For
 X11, you can install a utility program @file{x11idle.c}, available in the
 @code{contrib/scripts} directory of the Org git distribution, or install the
diff --git a/doc/misc/tramp.texi b/doc/misc/tramp.texi
index 5ce10d298c0..dae514033f8 100644
--- a/doc/misc/tramp.texi
+++ b/doc/misc/tramp.texi
@@ -977,7 +977,7 @@ active, @pxref{Top, , D-Bus, dbus}.
 @cindex afp method
 
 This method is for connecting to remote hosts with the Apple Filing
-Protocol for accessing files on Mac OS X volumes.  @value{tramp} access
+Protocol for accessing files on macOS volumes.  @value{tramp} access
 syntax requires a leading volume (share) name, for example:
 @file{@trampfn{afp,user@@host,/volume}}.
 
diff --git a/etc/DISTRIB b/etc/DISTRIB
index 7c0cd4cbaca..237e7f265f9 100644
--- a/etc/DISTRIB
+++ b/etc/DISTRIB
@@ -31,8 +31,8 @@ manuals, including the Emacs manual, are available from the FSF's
 online store at http://shop.fsf.org.
 
 Emacs has been run on GNU/Linux, FreeBSD, NetBSD, OpenBSD, and on many
-Unix systems, on a variety of types of cpu, as well as on MSDOS,
-Windows and MacOS.  See the file 'etc/MACHINES' in the Emacs
+Unix systems, on a variety of types of CPU, as well as on MS-DOS,
+MS-Windows and macOS.  See the file 'etc/MACHINES' in the Emacs
 distribution for a full list of machines that GNU Emacs has been tested
 on, with machine-specific installation notes and warnings.
 
diff --git a/etc/MACHINES b/etc/MACHINES
index 085f169e85b..fcab23c7b53 100644
--- a/etc/MACHINES
+++ b/etc/MACHINES
@@ -64,9 +64,9 @@ the list at the end of this file.
   This was tested on a little-endian sh4 system (cpu type SH7751R) running
   Gentoo Linux 2008.0.
 
-** Mac OS X
+** macOS
 
-  Version 10.6 or newer.  PowerPC is not supported.
+  Mac OS X 10.6 or newer.  PowerPC is not supported.
   For installation instructions see the file nextstep/INSTALL.
 
 ** Microsoft Windows
diff --git a/etc/NEWS b/etc/NEWS
index a5bcb8dabdc..f6792431907 100644
--- a/etc/NEWS
+++ b/etc/NEWS
@@ -88,7 +88,7 @@ If gnustep-config is not available, the old heuristics are used.
 unless gfile is explicitly requested via --with-file-notification='gfile'.
 
 ** 'configure' detects the kqueue file notification library on *BSD
-and Mac OS X machines.
+and macOS machines.
 
 ** The configure option '--with-pkg-config-prog' has been removed.
 Use './configure PKG_CONFIG=/full/name/of/pkg-config' if you need to.
@@ -202,10 +202,10 @@ the 'network-security-level' variable.
 
 ** 'x-select-enable-clipboard' is renamed 'select-enable-clipboard'
 and 'x-select-enable-primary' is renamed 'select-enable-primary'.
-Additionally they both now apply to all systems (OSX, GNUstep, Windows, you
-name it), with the proviso that on some systems (e.g. Windows)
-'select-enable-primary' is ineffective since the system doesn't
-have the equivalent of a primary selection.
+Additionally they both now apply to all systems (macOS, GNUstep,
+MS-Windows, you name it), with the proviso that on some systems (e.g.,
+MS-Windows) 'select-enable-primary' is ineffective since the system
+doesn't have the equivalent of a primary selection.
 
 ** New option 'switch-to-buffer-in-dedicated-window' allows you to
 customize how 'switch-to-buffer' proceeds interactively when the
@@ -817,7 +817,7 @@ PLIST will contain a :peer element that has the output of
 
 ** Tramp
 
-*** New connection method "afp", which allows you to access Mac OS X
+*** New connection method "afp", which allows you to access macOS
 volumes via the Apple Filing Protocol.
 
 *** New connection method "nc", which allows you to access dumb
@@ -1076,7 +1076,7 @@ See <http://debbugs.gnu.org/22814>.
 
 ** File Notifications
 
-*** The kqueue library is integrated for *BSD and Mac OS X machines.
+*** The kqueue library is integrated for *BSD and macOS machines.
 
 *** The new event 'stopped' signals, that a file notification watch is
 not active any longer.
@@ -1743,19 +1743,19 @@ of Windows starting with Windows 9X.
 ** The byte counts in etags-generated TAGS files are now the same on
 MS-Windows as they are on other platforms.
 
-** On OS X, configure creates a Cocoa ("Nextstep") build by default.
+** On macOS, configure creates a Cocoa ("Nextstep") build by default.
 Pass '--without-ns' to configure to create an X11 build, the old default.
 
-** OS X 10.5 or older is no longer supported.
+** Mac OS X 10.5 or older is no longer supported.
 
-** OS X on PowerPC is no longer supported.
+** Mac OS X on PowerPC is no longer supported.
 
 ** New variable 'ns-use-fullscreen-animation' controls animation for
 non-native NS fullscreen.  The default is nil.  Set to t to enable
-animation when entering and leaving fullscreen.  For native OSX fullscreen
-this has no effect.
+animation when entering and leaving fullscreen.  For native macOS
+fullscreen this has no effect.
 
-** On the OS X Cocoa ("Nextstep") port, multicolor font (such as color
+** On the macOS Cocoa ("Nextstep") port, multicolor font (such as color
 emoji) display is disabled.  This feature was accidentally added when
 Emacs 24.4 included the new Core Text based font backend code that was
 originally implemented for a non-mainline port.  This will be enabled
diff --git a/etc/NEWS.22 b/etc/NEWS.22
index 1bc4967d6ab..5e414f18d64 100644
--- a/etc/NEWS.22
+++ b/etc/NEWS.22
@@ -262,7 +262,7 @@ item was added to the menu bar to make it easily accessible
 You no longer need to download a separate tarball in order to build
 Emacs with Leim.
 
-** Support for MacOS X was added.
+** Support for Mac OS X was added.
 See the files mac/README and mac/INSTALL for build instructions.
 
 ** Mac OS 9 port now uses the Carbon API by default.  You can also
@@ -3390,7 +3390,7 @@ obsolete; use `dframe-update-speed' instead.
 
 *** display-battery-mode replaces display-battery.
 
-*** battery.el now works on recent versions of OS X.
+*** battery.el now works on recent versions of Mac OS X.
 
 ** Games
 
diff --git a/etc/NEWS.24 b/etc/NEWS.24
index df2e11f08e7..08021f4ee04 100644
--- a/etc/NEWS.24
+++ b/etc/NEWS.24
@@ -84,7 +84,7 @@ It is no longer needed, as the crt*.o files are no longer linked specially.
 ** Directories passed to configure option `--enable-locallisppath' are
 no longer created during installation.
 
-** Emacs for Nextstep (Mac OS X, GNUstep) can be built with ImageMagick support.
+** Emacs for Nextstep (OS X, GNUstep) can be built with ImageMagick support.
 This requires pkg-config to be available at build time.
 
 
@@ -1559,7 +1559,7 @@ The previous binding, introduced in Emacs 24.1, was a mistake, because
 
 *** New input method `vietnamese-vni'.
 
-** Nextstep (GNUstep / Mac OS X) port
+** Nextstep (GNUstep / OS X) port
 
 *** Support for fullscreen and the frame parameter fullscreen.
 
@@ -2373,9 +2373,9 @@ Emacs now supports `mouse-highlight', help-echo (in the echo area), and
 ** On MS Windows, you can pass `--without-libxml2' to configure.bat to omit
 support for libxml2, even if its presence is detected.
 
-** On Mac OS X, the Nextstep port requires OS X 10.4 or later.
+** On OS X, the Nextstep port requires Mac OS X 10.4 or later.
 
-** On Mac OS X, configure no longer automatically adds the Fink "/sw"
+** On OS X, configure no longer automatically adds the Fink "/sw"
 directories to the search path.  You must add them yourself if you want them.
 
 
@@ -3833,7 +3833,7 @@ and also when HOME is set to C:\ by default.
 (It is only used internally in the Emacs C code.)
 
 ** Customize ns-auto-hide-menu-bar to have the menu-bar hidden, but
-reappear on mouse-over.  (Requires OS X 10.6 or later.)
+reappear on mouse-over.  (Requires Mac OS X 10.6 or later.)
 
 ** On Mac OS X, dragging a file into Emacs visits the file, like on
 other platforms, rather than inserting its contents into the buffer.
diff --git a/etc/NEXTSTEP b/etc/NEXTSTEP
index ad2ab959e6d..60c49ad8c7e 100644
--- a/etc/NEXTSTEP
+++ b/etc/NEXTSTEP
@@ -3,8 +3,8 @@ See the end of the file for license conditions.
 
 This file contains information about GNU Emacs on "Nextstep" platforms.
 The Nextstep support code works on many POSIX systems (and possibly
-W32) using the GNUstep libraries, and on MacOS X systems using the
-Cocoa libraries.
+W32) using the GNUstep libraries, and on macOS systems using the Cocoa
+libraries.
 
 Background
 ----------
@@ -17,9 +17,9 @@ system in the late 1980's.  Later on, in collaboration with Sun, this
 API was published as a specification called OpenStep.  The GNUstep
 project started in the early 1990's to provide a free implementation
 of this API.  Later on, Apple bought NeXT (some would say "NeXT bought
-Apple") and made OpenStep the basis of OS X, calling the API "Cocoa".
-Since then, Cocoa has evolved beyond the OpenStep specification, and
-GNUstep has followed it.
+Apple") and made OpenStep the basis of Mac OS X, calling the API
+"Cocoa".  Since then, Cocoa has evolved beyond the OpenStep
+specification, and GNUstep has followed it.
 
 Thus, calling this port "OpenStep" is not technically accurate, and in
 the absence of any other determinant, we are using the term
@@ -30,8 +30,8 @@ begin with the letters "NS".
 (See http://en.wikipedia.org/wiki/Nextstep)
 
 This Emacs port was first released in the early 1990's on the NeXT
-computer, and was successively updated to OpenStep, Rhapsody, OS X,
-and then finally GNUstep, tracking GNU emacs core releases in the
+computer, and was successively updated to OpenStep, Rhapsody, Mac OS
+X, and then finally GNUstep, tracking GNU Emacs core releases in the
 meantime.
 
 
@@ -62,13 +62,13 @@ Release History
 
 1999/05/??      6.0b3           Scott Bender: "OS X Server", Emacs 20.3.
 
-2001/06/25      7.0             Ported to MacOS X (10.1) by Christophe de
+2001/06/25      7.0             Ported to Mac OS X (10.1) by Christophe de
                                 Dinechin. Release based on Emacs 20.7. Hosting
                                 moved to SourceForge.
 
 2002/01/03      7.0.1           Bug fixes.
 
-2002/08/27      7.0.2           Jaguar (OS X 10.2) support. Added an autoconf
+2002/08/27      7.0.2           Jaguar (Mac OS X 10.2) support. Added autoconf
                                 option for sys_nerr being in stdio. Added
                                 libncurses to the build libraries. Fixed a
                                 problem with ns-alternate-is-meta. Changed the
@@ -76,7 +76,7 @@ Release History
 
 2004/10/07      8.0-pre1        Ported to GNUstep by Adrian Robert.
 
-2004/11/04      8.0-pre2        Restored functionality on OS X (menu code
+2004/11/04      8.0-pre2        Restored functionality on Mac OS X (menu code
                                 cleanup).  Improved scrollbar handling and
                                 paste from other applications.  File icons
                                 obtained properly from NSWorkspace.  Dropped
@@ -116,7 +116,8 @@ Release History
                                 and Planner go away.  Improved scrollbar
                                 handling and rendering speed.  Color panel
                                 and other bug fixes. mac-fix-env utility.
-                                Font handling improvements (OS X 10.3, 10.4):
+                                Font handling improvements (Mac OS X 10.3,
+                                10.4):
                                 - heed 'GSFontAntiAlias' default
                                 - heed system antialiasing threshold
                                 - added 'UseQuickdrawSmoothing' default to
@@ -150,8 +151,9 @@ Release History
                                 handling improved.  Fixed some portability
                                 problems on Tiger and Puma.
 
-2005/09/12      8.0             Bundled ispell on OS X.  Minor bug fixes and
-                                stability improvements.  Compiles under gcc-4.
+2005/09/12      8.0             Bundled ispell on Mac OS X.  Minor bug fixes
+                                and stability improvements.  Compiles under
+                                gcc-4.
 
 2005/09/26      8.0.1           Correct clipped rendering for synthetic
                                 italics. Include the info directory.
@@ -247,7 +249,7 @@ Christian Limpach
 Scott Bender
     OpenStep, Rhapsody ports
 Christophe de Dinechin
-    MacOS X port
+    macOS port
 Adrian Robert
     GNUstep port, update Emacs 20 -> 21+
 
diff --git a/etc/ORG-NEWS b/etc/ORG-NEWS
index 9d80139fa94..8d8c0c604a7 100644
--- a/etc/ORG-NEWS
+++ b/etc/ORG-NEWS
@@ -952,7 +952,7 @@ instead of requiring each Babel library one by one.
 - New option [[doc:org-gnus-no-server][org-gnus-no-server]] to start Gnus with =gnus-no-server=
 - Org is now distributed with =htmlize.el= version 1.43
 - ~org-drill.el~ has been updated to version 2.3.7
-- ~org-mac-iCal.el~ now supports MacOSX version up to 10.8
+- ~org-mac-iCal.el~ now supports OS X versions up to 10.8
 - Various improvements to ~org-contacts.el~ and =orgpan.el=
 
 ** Outside Org
diff --git a/etc/PROBLEMS b/etc/PROBLEMS
index 008f5a15310..9904339be40 100644
--- a/etc/PROBLEMS
+++ b/etc/PROBLEMS
@@ -604,7 +604,7 @@ See <http://debbugs.gnu.org/22814>.
 When you have a large number of buffers running auto-revert-mode, and
 Emacs is configured to use the kqueue file notification library, it
 uses an own file descriptor for every watched file.  On systems with a
-small limit of file descriptors allowed per process, like OS X, you
+small limit of file descriptors allowed per process, like macOS, you
 could run out of file descriptors.  You won't be able to open new files.
 
 auto-revert-use-notify is set to nil in global-auto-revert-mode, therefore.
diff --git a/etc/TODO b/etc/TODO
index 48c1654aa1f..84c1b6d8ffd 100644
--- a/etc/TODO
+++ b/etc/TODO
@@ -700,7 +700,7 @@ resize the frame.
 **** Support 'proced' (implement 'process-attributes')
 
 Unfortunately, a user-level process like Emacs does not have the
-privileges to get information about other processes under OS X.
+privileges to get information about other processes under macOS.
 
 There are other ways to do this:
 
@@ -711,7 +711,7 @@ There are other ways to do this:
  3) Ask the user to self-sign Emacs, if this feature is of interest.
 
 Anders Lindgren <andlind@gmail.com> has implemented
-'process-attributes' for OS X, which currently only work when
+'process-attributes' for macOS, which currently only work when
 running Emacs as root.
 
 See this article by Bozhidar Batsov for an overview of Proced:
@@ -724,11 +724,11 @@ even though Emacs allows a user to customize such features.
 
 *** New features
 
-This section contains features unique to Nextstep and/or OS X.
+This section contains features unique to Nextstep and/or macOS.
 
 **** PressAndHold for writing accented character
 
-On OS X, many application support the press and hold pattern to
+On macOS, many application support the press and hold pattern to
 invoke a menu of accented characters.  (See example at
 https://support.apple.com/en-us/HT201586 .)
 
@@ -741,7 +741,7 @@ implemented in Emacs for a free system.
 
 **** Floating scroll bars
 
-In modern OS X applications, the scroll bar often floats over the
+In modern macOS applications, the scroll bar often floats over the
 content, and is invisible unless actually used.  This makes the user
 interface less cluttered and more area could be used to contain text.
 
@@ -804,7 +804,7 @@ This section contains issues where there is an ongoing debate.
 **** Key bindings of CMD and ALT
 
 Currently in the "ns" port, ALT is bound to Meta and CMD is bound to
-Super -- allowing the user to use typical OS X commands like CMD-A to
+Super -- allowing the user to use typical macOS commands like CMD-A to
 mark everything.
 
 Unfortunately, when using an international keyboard, you can't type
@@ -852,9 +852,10 @@ Emacs can be build in a number of different ways.  For each feature,
 consider if is really is "NS" specific, or if it should be applied to
 all build versions.
 
-- With the "NS" interface.  This is the normal way to build Emacs on OS X.
+- With the "NS" interface.  This is the normal way to build Emacs on
+  macOS.
 
-- With the "X11" interface.  On OS X, this is mainly of interest to
+- With the "X11" interface.  On macOS, this is mainly of interest to
   developers of Emacs to get a "reference" interface implementations.
   However, it might be of interest for people working remotely, as X11
   applications can be used over a network connection.
@@ -863,12 +864,12 @@ all build versions.
 
 *** Bugs
 
-**** Incorrect translation of Super modifier with Ctrl or Meta on OS X
+**** Incorrect translation of Super modifier with Ctrl or Meta on macOS
 
 When pressing 'M-s-a', Emacs replies "M-s-å is undefined".  What
 happened is a mix of Emacs view that Meta and Super has been pressed,
-and OS X view that ALT-a should yield "å" (U+00E5 LATIN SMALL LETTER A
-WITH RING ABOVE).
+and macOS view that ALT-a should yield "å" (U+00E5 LATIN SMALL LETTER
+A WITH RING ABOVE).
 
 The bug reports suggest two different patches; unfortunately, neither
 works properly.  For example:
diff --git a/lib-src/Makefile.in b/lib-src/Makefile.in
index 5fa152ae5bf..2aaec25a5a3 100644
--- a/lib-src/Makefile.in
+++ b/lib-src/Makefile.in
@@ -75,7 +75,7 @@ am__v_at_1 =
 
 # ==================== Where To Install Things ====================
 
-# Location to install Emacs.app under GNUstep / Mac OS X.
+# Location to install Emacs.app under GNUstep / macOS.
 # Later values may use this.
 ns_appbindir=@ns_appbindir@
 
diff --git a/lisp/arc-mode.el b/lisp/arc-mode.el
index b5373c607d4..c42ca813e96 100644
--- a/lisp/arc-mode.el
+++ b/lisp/arc-mode.el
@@ -1646,7 +1646,7 @@ This doesn't recover lost files, it just undoes changes in the buffer itself."
         ;;   converts "\" to "/".
         ;; - For 0 generic: generic_to_unix_filename() downcases if there's
         ;;   no lower case already present, and converts "\" to "/".
-        ;; - For 'm' MacOS: macos_to_unix_filename() changes "/" to ":" and
+        ;; - For 'm' macOS: macos_to_unix_filename() changes "/" to ":" and
         ;;   ":" to "/"
         (setq fiddle (cond ((= ?M osid) t)
                            ((= 0 osid)  (string= efnname (upcase efnname)))))
diff --git a/lisp/battery.el b/lisp/battery.el
index b5e312f6c3e..20f3017fc45 100644
--- a/lisp/battery.el
+++ b/lisp/battery.el
@@ -22,10 +22,10 @@
 
 ;;; Commentary:
 
-;; There is at present support for GNU/Linux, OS X and Windows.  This
+;; There is at present support for GNU/Linux, macOS and Windows.  This
 ;; library supports both the `/proc/apm' file format of Linux version
 ;; 1.3.58 or newer and the `/proc/acpi/' directory structure of Linux
-;; 2.4.20 and 2.6.  Darwin (OS X) is supported by using the `pmset'
+;; 2.4.20 and 2.6.  Darwin (macOS) is supported by using the `pmset'
 ;; program.  Windows is supported by the GetSystemPowerStatus API call.
 
 ;;; Code:
@@ -600,7 +600,7 @@ The following %-sequences are provided:
           (cons ?t (or remaining-time "N/A")))))
 
 
-;;; `pmset' interface for Darwin (OS X).
+;;; `pmset' interface for Darwin (macOS).
 
 (defun battery-pmset ()
   "Get battery status information using `pmset'.
diff --git a/lisp/cedet/semantic/bovine/gcc.el b/lisp/cedet/semantic/bovine/gcc.el
index ec292395f12..b56b268ca0d 100644
--- a/lisp/cedet/semantic/bovine/gcc.el
+++ b/lisp/cedet/semantic/bovine/gcc.el
@@ -225,7 +225,7 @@ It should also include other symbols GCC was compiled with.")
         (setq semantic-lex-c-preprocessor-symbol-map nil))
     (dolist (D defines)
       (add-to-list 'semantic-lex-c-preprocessor-symbol-map D))
-    ;; Needed for parsing OS X libc
+    ;; Needed for parsing macOS libc
     (when (eq system-type 'darwin)
       (add-to-list 'semantic-lex-c-preprocessor-symbol-map '("__i386__" . "")))
     (when (featurep 'semantic/bovine/c)
diff --git a/lisp/faces.el b/lisp/faces.el
index b1ea0f0fc34..a84edab3615 100644
--- a/lisp/faces.el
+++ b/lisp/faces.el
@@ -108,7 +108,7 @@ a font height that isn't optimal."
      "Courier 10 Pitch"
      ;; This looks good on MS-Windows and OS X.
      "Consolas"
-     ;; This looks good on OS X.  "Courier" looks good too, but is
+     ;; This looks good on macOS.  "Courier" looks good too, but is
      ;; jagged on GNU/Linux and so is listed later as "courier".
      "Courier Std"
      ;; Although these are anti-aliased, they are a bit faint compared
diff --git a/lisp/gnus/auth-source.el b/lisp/gnus/auth-source.el
index 52765ce6b31..df8f61ff380 100644
--- a/lisp/gnus/auth-source.el
+++ b/lisp/gnus/auth-source.el
@@ -423,13 +423,13 @@ with \"[a/b/c] \" if CHOICES is \(?a ?b ?c)."
     ;; Keychain collection matching any user, host, and protocol
     ((eq entry 'macos-keychain-generic)
      (auth-source-backend-parse '(:source (:macos-keychain-generic default))))
-    ;; take macos-keychain-internet:XYZ and recurse to get it as MacOS
+    ;; take macos-keychain-internet:XYZ and recurse to get it as macOS
     ;; Keychain "XYZ" matching any user, host, and protocol
     ((and (stringp entry) (string-match "^macos-keychain-internet:\\(.+\\)"
                                         entry))
      (auth-source-backend-parse `(:source (:macos-keychain-internet
                                            ,(match-string 1 entry)))))
-    ;; take macos-keychain-generic:XYZ and recurse to get it as MacOS
+    ;; take macos-keychain-generic:XYZ and recurse to get it as macOS
     ;; Keychain "XYZ" matching any user, host, and protocol
     ((and (stringp entry) (string-match "^macos-keychain-generic:\\(.+\\)"
                                         entry))
@@ -458,7 +458,7 @@ with \"[a/b/c] \" if CHOICES is \(?a ?b ?c)."
         :search-function #'auth-source-netrc-search
         :create-function #'auth-source-netrc-create)))
 
-    ;; the MacOS Keychain
+    ;; the macOS Keychain
     ((and
       (not (null (plist-get entry :source))) ; the source must not be nil
       (listp (plist-get entry :source))      ; and it must be a list
@@ -1666,7 +1666,7 @@ authentication tokens:
                                     &key backend create delete
                                     type max
                                     &allow-other-keys)
-  "Search the MacOS Keychain; spec is like `auth-source'.
+  "Search the macOS Keychain; spec is like `auth-source'.
 
 All search keys must match exactly.  If you need substring
 matching, do a wider search and narrow it down yourself.
@@ -1688,13 +1688,13 @@ Similarly, :host maps to \"-c HOST\" (the \"creator\" keychain
 field), :user maps to \"-a USER\", and :port maps to \"-s PORT\".
 
 Here's an example that looks for the first item in the default
-generic MacOS Keychain:
+generic macOS Keychain:
 
  (let ((auth-sources \\='(macos-keychain-generic)))
     (auth-source-search :max 1)
 
 Here's another that looks for the first item in the internet
-MacOS Keychain collection whose label is `gnus':
+macOS Keychain collection whose label is `gnus':
 
  (let ((auth-sources \\='(macos-keychain-internet)))
     (auth-source-search :max 1 :label \"gnus\")
@@ -1707,11 +1707,11 @@ entries for git.gnus.org:
 "
   ;; TODO
   (assert (not create) nil
-          "The MacOS Keychain auth-source backend doesn't support creation yet")
+          "The macOS Keychain auth-source backend doesn't support creation yet")
   ;; TODO
   ;; (macos-keychain-delete-item coll elt)
   (assert (not delete) nil
-          "The MacOS Keychain auth-source backend doesn't support deletion yet")
+          "The macOS Keychain auth-source backend doesn't support deletion yet")
 
   (let* ((coll (oref backend source))
          (max (or max 5000))     ; sanity check: default to stop at 5K
diff --git a/lisp/international/mule-cmds.el b/lisp/international/mule-cmds.el
index e7c7049cd0a..5008fd5f27b 100644
--- a/lisp/international/mule-cmds.el
+++ b/lisp/international/mule-cmds.el
@@ -2723,7 +2723,7 @@ See also `locale-charset-language-names', `locale-language-names',
       ;; On Darwin, file names are always encoded in utf-8, no matter
       ;; the locale.
       (setq default-file-name-coding-system 'utf-8)
-      ;; Mac OS X's Terminal.app by default uses utf-8 regardless of
+      ;; macOS's Terminal.app by default uses utf-8 regardless of
       ;; the locale.
       (when (and (null window-system)
                  (equal (getenv "TERM_PROGRAM" frame) "Apple_Terminal"))
diff --git a/lisp/international/ucs-normalize.el b/lisp/international/ucs-normalize.el
index 1e247c5dba5..29cd042eee9 100644
--- a/lisp/international/ucs-normalize.el
+++ b/lisp/international/ucs-normalize.el
@@ -624,7 +624,7 @@ COMPOSITION-PREDICATE will be used to compose region."
 
 ;;; coding-system definition
 (define-coding-system 'utf-8-hfs
-  "UTF-8 based coding system for MacOS HFS file names.
+  "UTF-8 based coding system for macOS HFS file names.
 The singleton characters in HFS normalization exclusion will not
 be decomposed."
   :coding-type 'utf-8
diff --git a/lisp/ls-lisp.el b/lisp/ls-lisp.el
index 85e91cdadc0..41587bfe144 100644
--- a/lisp/ls-lisp.el
+++ b/lisp/ls-lisp.el
@@ -75,7 +75,7 @@
         ((memq system-type '(hpux usg-unix-v irix berkeley-unix))
          'UNIX))        ; very similar to GNU
   ;; Anything else defaults to nil, meaning GNU.
-  "Platform to emulate: GNU (default), MacOS, MS-Windows, UNIX.
+  "Platform to emulate: GNU (default), macOS, MS-Windows, UNIX.
 Corresponding value is one of: nil, `MacOS', `MS-Windows', `UNIX'.
 Set this to your preferred value; it need not match the actual platform
 you are using.
diff --git a/lisp/mail/emacsbug.el b/lisp/mail/emacsbug.el
index ce3c50bce2b..86aefe4a6dd 100644
--- a/lisp/mail/emacsbug.el
+++ b/lisp/mail/emacsbug.el
@@ -72,7 +72,7 @@
 (defvar message-strip-special-text-properties)
 
 (defun report-emacs-bug-can-use-osx-open ()
-  "Return non-nil if the OS X \"open\" command is available for mailing."
+  "Return non-nil if the macOS \"open\" command is available for mailing."
   (and (featurep 'ns)
        (equal (executable-find "open") "/usr/bin/open")
        (memq system-type '(darwin))))
@@ -107,7 +107,7 @@ This requires you to be running either Gnome, KDE, or Xfce4."
 
 (defun report-emacs-bug-insert-to-mailer ()
   "Send the message to your preferred mail client.
-This requires either the OS X \"open\" command, or the freedesktop
+This requires either the macOS \"open\" command, or the freedesktop
 \"xdg-email\" command to be available."
   (interactive)
   (save-excursion
diff --git a/lisp/man.el b/lisp/man.el
index 5acf90baf28..94b9e0d04da 100644
--- a/lisp/man.el
+++ b/lisp/man.el
@@ -887,7 +887,7 @@ test/automated/man-tests.el in the emacs repository."
           (setq default-directory "/") ;; in case inherited doesn't exist
           ;; Actually for my `man' the arg is a regexp.
           ;; POSIX says it must be ERE and "man-db" seems to agree,
-          ;; whereas under MacOSX it seems to be BRE-style and doesn't
+          ;; whereas under macOS it seems to be BRE-style and doesn't
           ;; accept backslashes at all.  Let's not bother to
           ;; quote anything.
           (let ((process-environment (copy-sequence process-environment)))
diff --git a/lisp/menu-bar.el b/lisp/menu-bar.el
index 640395e8d7d..ba1bf34d1a5 100644
--- a/lisp/menu-bar.el
+++ b/lisp/menu-bar.el
@@ -1865,7 +1865,7 @@ key, a click, or a menu-item"))
       '(menu-item "Emacs Tutorial" help-with-tutorial
                   :help "Learn how to use Emacs"))
 
-    ;; In OS X it's in the app menu already.
+    ;; In macOS it's in the app menu already.
     ;; FIXME? There already is an "About Emacs" (sans ...) entry in the Help menu.
     (and (featurep 'ns)
          (not (eq system-type 'darwin))
diff --git a/lisp/net/ange-ftp.el b/lisp/net/ange-ftp.el
index d5c03e3f4ae..239da7829df 100644
--- a/lisp/net/ange-ftp.el
+++ b/lisp/net/ange-ftp.el
@@ -740,7 +740,7 @@ These mean that the FTP process should be (or already has been) killed."
   :type 'regexp)
 
 (defcustom ange-ftp-potential-error-msgs
-  ;; On Mac OS X we sometimes get things like:
+  ;; On macOS we sometimes get things like:
   ;;
   ;;     ftp> open ftp.nluug.nl
   ;;     Trying 2001:610:1:80aa:192:87:102:36...
diff --git a/lisp/net/browse-url.el b/lisp/net/browse-url.el
index be859283891..68258d41666 100644
--- a/lisp/net/browse-url.el
+++ b/lisp/net/browse-url.el
@@ -44,7 +44,7 @@
 ;; browse-url-text-*                  Any text browser     0
 ;; browse-url-generic                 arbitrary
 ;; browse-url-default-windows-browser MS-Windows browser
-;; browse-url-default-macosx-browser  Mac OS X browser
+;; browse-url-default-macosx-browser  macOS browser
 ;; browse-url-xdg-open                Free Desktop xdg-open on Gnome, KDE, Xfce4, LXDE
 ;; browse-url-kde                     KDE konqueror (kfm)
 ;; browse-url-elinks                  Elinks      Don't know (tried with 0.12.GIT)
@@ -162,7 +162,7 @@ regexp should probably be \".\" to specify a default browser."
                          :value browse-url-generic)
           (function-item :tag "Default Windows browser"
                          :value browse-url-default-windows-browser)
-          (function-item :tag "Default Mac OS X browser"
+          (function-item :tag "Default macOS browser"
                          :value browse-url-default-macosx-browser)
           (function-item :tag "Default browser"
                          :value browse-url-default-browser)
@@ -870,7 +870,7 @@ The optional NEW-WINDOW argument is not used."
         (t (w32-shell-execute "open" url))))
 
 (defun browse-url-default-macosx-browser (url &optional _new-window)
-  "Invoke the MacOS X system's default Web browser.
+  "Invoke the macOS system's default Web browser.
 The optional NEW-WINDOW argument is not used"
   (interactive (browse-url-interactive-arg "URL: "))
   (start-process (concat "open " url) nil "open" url))
diff --git a/lisp/net/tramp-sh.el b/lisp/net/tramp-sh.el
index 2983d402fa3..842b1ce2880 100644
--- a/lisp/net/tramp-sh.el
+++ b/lisp/net/tramp-sh.el
@@ -1272,7 +1272,7 @@ target of the symlink differ."
                  res-uid res-gid res-size res-symlink-target)
     (tramp-message vec 5 "file attributes with ls: %s" localname)
     ;; We cannot send all three commands combined, it could exceed
-    ;; NAME_MAX or PATH_MAX.  Happened on Mac OS X, for example.
+    ;; NAME_MAX or PATH_MAX.  Happened on macOS, for example.
     (when (or (tramp-send-command-and-check
                vec
                (format "%s %s"
@@ -4263,7 +4263,7 @@ process to set up.  VEC specifies the connection."
             (when (search-forward "\r" nil t)
               (setq cs-decode (tramp-compat-coding-system-change-eol-conversion
                                cs-decode 'dos)))
-            ;; Special setting for Mac OS X.
+            ;; Special setting for macOS.
             (when (and (string-match "^Darwin" uname)
                        (memq 'utf-8-hfs (coding-system-list)))
               (setq cs-decode 'utf-8-hfs
@@ -4325,7 +4325,7 @@ process to set up.  VEC specifies the connection."
         (tramp-send-command vec "stty tabs" t)
       (tramp-send-command vec "stty tab0" t))
 
-    ;; Set utf8 encoding.  Needed for Mac OS X, for example.  This is
+    ;; Set utf8 encoding.  Needed for macOS, for example.  This is
     ;; non-POSIX, so we must expect errors on some systems.
     (tramp-send-command vec "stty iutf8 2>/dev/null" t)
 
diff --git a/lisp/net/tramp.el b/lisp/net/tramp.el
index cb8e4d4d4c3..5d8081cd815 100644
--- a/lisp/net/tramp.el
+++ b/lisp/net/tramp.el
@@ -1018,7 +1018,7 @@ this variable to be set as well."
   :type '(choice (const nil) integer))
 
 ;; Logging in to a remote host normally requires obtaining a pty.  But
-;; Emacs on MacOS X has process-connection-type set to nil by default,
+;; Emacs on macOS has process-connection-type set to nil by default,
 ;; so on those systems Tramp doesn't obtain a pty.  Here, we allow
 ;; for an override of the system default.
 (defcustom tramp-process-connection-type t
diff --git a/lisp/org/org.el b/lisp/org/org.el
index 13e4a222131..eb01426533d 100644
--- a/lisp/org/org.el
+++ b/lisp/org/org.el
@@ -1937,7 +1937,7 @@ See `org-file-apps'.")
     ("eps.gz" . "gv %s")
     ("dvi"    . "xdvi %s")
     ("fig"    . "xfig %s"))
-  "Default file applications on a MacOS X system.
+  "Default file applications on a macOS system.
 The system \"open\" is known as a default, but we use X11 applications
 for some files for which the OS does not have a good default.
 See `org-file-apps'.")
@@ -2012,7 +2012,7 @@ file identifier are
                (\"html\" . default) to the list as well.
  t             Default for files not matched by any of the other options.
  `system'      The system command to open files, like `open' on Windows
-               and Mac OS X, and mailcap under GNU/Linux.  This is the command
+               and macOS, and mailcap under GNU/Linux.  This is the command
                that will be selected if you call `C-c C-o' with a double
                \\[universal-argument] \\[universal-argument] prefix.
 
diff --git a/lisp/printing.el b/lisp/printing.el
index d9cc2a3614a..72f825fcb89 100644
--- a/lisp/printing.el
+++ b/lisp/printing.el
@@ -2272,7 +2272,7 @@ Useful links:
 * gv 3.5, June 1997
   `http://www.cs.wisc.edu/~ghost/gv/gv_doc/gv.html'
 
-* MacGSView (MacOS)
+* MacGSView (Mac OS)
   `http://www.cs.wisc.edu/~ghost/macos/index.htm'
 "
   :type '(string :tag "Ghostview Utility")
diff --git a/lisp/progmodes/gdb-mi.el b/lisp/progmodes/gdb-mi.el
index d243650d73a..978b81699fc 100644
--- a/lisp/progmodes/gdb-mi.el
+++ b/lisp/progmodes/gdb-mi.el
@@ -69,12 +69,12 @@
 ;;   2) Use MinGW GDB instead.
 ;;   3) Use cygwin-mount.el
 
-;;; Mac OSX:
+;;; macOS:
 
-;; GDB in Emacs on Mac OSX works best with FSF GDB as Apple have made
-;; some changes to the version that they include as part of Mac OSX.
-;; This requires GDB version 7.0 or later (estimated release date Aug 2009)
-;; as earlier versions do not compile on Mac OSX.
+;; GDB in Emacs on macOS works best with FSF GDB as Apple have made
+;; some changes to the version that they include as part of macOS.
+;; This requires GDB version 7.0 or later as earlier versions do not
+;; compile on macOS.
 
 ;;; Known Bugs:
 
diff --git a/lisp/progmodes/idlwave.el b/lisp/progmodes/idlwave.el
index 9cb2ca74063..bc607ac4019 100644
--- a/lisp/progmodes/idlwave.el
+++ b/lisp/progmodes/idlwave.el
@@ -420,22 +420,22 @@ A value of t means to show all source files."
   :type 'integer)
 
 (defcustom idlwave-library-path nil
-  "Library path for Windows and MacOS (OS9).  Not needed under UNIX.
+  "Library path for Windows and Mac OS (OS9).  Not needed under UNIX.
 When selecting the directories to scan for IDL user catalog routine
 info, IDLWAVE can, under UNIX, query the shell for the exact search
-path \(the value of !PATH).  However, under Windows and MacOS
-\(pre-OSX), the IDLWAVE shell does not work.  In this case, this
-variable can be set to specify the paths where IDLWAVE can find PRO
-files.  The shell will only be asked for a list of paths when this
-variable is nil.  The value is a list of directories.  A directory
+path (the value of !PATH).  However, under MS-Windows, the
+IDLWAVE shell does not work.  In this case, this variable can be
+set to specify the paths where IDLWAVE can find PRO files.  The
+shell will only be asked for a list of paths when this variable
+is nil.  The value is a list of directories.  A directory
 preceded by a `+' will be searched recursively.  If you set this
-variable on a UNIX system, the shell will not be queried.  See also
-`idlwave-system-directory'."
+variable on a UNIX system, the shell will not be queried.  See
+also `idlwave-system-directory'."
   :group 'idlwave-routine-info
   :type '(repeat (directory)))
 
 (defcustom idlwave-system-directory ""
-  "The IDL system directory for Windows and MacOS.  Not needed under
+  "The IDL system directory for Windows and Mac OS.  Not needed under
 UNIX.  Set this to the value of the `!DIR' system variable in IDL.
 IDLWAVE uses this to find out which of the library routines belong to
 the official system library.  All files inside the `lib' subdirectory
diff --git a/lisp/progmodes/python.el b/lisp/progmodes/python.el
index 3fae3987b22..8ec9febe5c9 100644
--- a/lisp/progmodes/python.el
+++ b/lisp/progmodes/python.el
@@ -2414,7 +2414,7 @@ banner and the initial prompt are received separately."
 (defun python-shell-comint-end-of-output-p (output)
   "Return non-nil if OUTPUT is ends with input prompt."
   (string-match
-   ;; XXX: It seems on OSX an extra carriage return is attached
+   ;; XXX: It seems on macOS an extra carriage return is attached
    ;; at the end of output, this handles that too.
    (concat
     "\r?\n?"
diff --git a/lisp/term/ns-win.el b/lisp/term/ns-win.el
index e737131d5bf..21bba480d02 100644
--- a/lisp/term/ns-win.el
+++ b/lisp/term/ns-win.el
@@ -1,4 +1,4 @@
-;;; ns-win.el --- lisp side of interface with NeXT/Open/GNUstep/MacOS X window system  -*- lexical-binding: t -*-
+;;; ns-win.el --- lisp side of interface with NeXT/Open/GNUstep/macOS window system  -*- lexical-binding: t -*-
 
 ;; Copyright (C) 1993-1994, 2005-2016 Free Software Foundation, Inc.
 
@@ -41,7 +41,7 @@
 ;;; Code:
 (eval-when-compile (require 'cl-lib))
 (or (featurep 'ns)
-    (error "%s: Loading ns-win.el but not compiled for GNUstep/MacOS"
+    (error "%s: Loading ns-win.el but not compiled for GNUstep/macOS"
            (invocation-name)))
 
 ;; Documentation-purposes only: actually loaded in loadup.el.
@@ -54,7 +54,7 @@
 (require 'ucs-normalize)
 
 (defgroup ns nil
-  "GNUstep/Mac OS X specific features."
+  "GNUstep/macOS specific features."
   :group 'environment)
 
 ;;;; Command line argument handling.
@@ -338,7 +338,7 @@ See `ns-insert-working-text'."
   (setq ns-working-overlay nil))
 
 
-;; OS X file system Unicode UTF-8 NFD (decomposed form) support.
+;; macOS file system Unicode UTF-8 NFD (decomposed form) support.
 (when (eq system-type 'darwin)
   ;; Used prior to Emacs 25.
   (define-coding-system-alias 'utf-8-nfd 'utf-8-hfs)
@@ -641,7 +641,7 @@ This function has been overloaded in Nextstep.")
   (set-frame-font ns-input-font))
 
 
-;; Default fontset for Mac OS X.  This is mainly here to show how a fontset
+;; Default fontset for macOS.  This is mainly here to show how a fontset
 ;; can be set up manually.  Ordinarily, fontsets are auto-created whenever
 ;; a font is chosen by
 (defvar ns-standard-fontset-spec
@@ -655,7 +655,7 @@ This function has been overloaded in Nextstep.")
              ",")
   "String of fontset spec of the standard fontset.
 This defines a fontset consisting of the Courier and other fonts that
-come with OS X.
+come with macOS.
 See the documentation of `create-fontset-from-fontset-spec' for the format.")
 
 (defvar ns-reg-to-script)               ; nsfont.m
@@ -892,7 +892,7 @@ See the documentation of `create-fontset-from-fontset-spec' for the format.")
                     (setq default-process-coding-system
                           '(utf-8-unix . utf-8-unix)))))
 
-  ;; OS X Lion introduces PressAndHold, which is unsupported by this port.
+  ;; Mac OS X Lion introduces PressAndHold, which is unsupported by this port.
   ;; See this thread for more details:
   ;; http://lists.gnu.org/archive/html/emacs-devel/2011-06/msg00505.html
   (ns-set-resource nil "ApplePressAndHoldEnabled" "NO")
diff --git a/lisp/term/xterm.el b/lisp/term/xterm.el
index 19eb37a51d6..880141bda12 100644
--- a/lisp/term/xterm.el
+++ b/lisp/term/xterm.el
@@ -771,7 +771,7 @@ We run the first FUNCTION whose STRING matches the input events."
       ;; Try to find out the type of terminal by sending a "Secondary
       ;; Device Attributes (DA)" query.
       (xterm--query "\e[>0c"
-                    ;; Some terminals (like OS X's Terminal.app) respond to
+                    ;; Some terminals (like macOS's Terminal.app) respond to
                     ;; this query as if it were a "Primary Device Attributes"
                     ;; query instead, so we should handle that too.
                     '(("\e[?" . xterm--version-handler)
diff --git a/lisp/textmodes/rst.el b/lisp/textmodes/rst.el
index 3d4854e89d6..aea8e7072ea 100644
--- a/lisp/textmodes/rst.el
+++ b/lisp/textmodes/rst.el
@@ -645,7 +645,7 @@ as well but give an additional message."
     ;;
     ;; The adjustment function that adorns or rotates a section title.
     (rst-define-key map [?\C-c ?\C-=] 'rst-adjust [?\C-c ?\C-a t])
-    (rst-define-key map [?\C-=] 'rst-adjust) ; Does not work on the Mac OSX and
+    (rst-define-key map [?\C-=] 'rst-adjust) ; Does not work on macOS and
                                              ; on consoles.
 
     ;; \C-c \C-a is the keymap for adornments.
diff --git a/lisp/vc/pcvs.el b/lisp/vc/pcvs.el
index 573feedd047..b0ad5ea588d 100644
--- a/lisp/vc/pcvs.el
+++ b/lisp/vc/pcvs.el
@@ -551,7 +551,7 @@ If non-nil, NEW means to create a new buffer no matter what."
                ;; is accessed via SSH, a bad interaction between libc,
                ;; CVS and SSH can lead to garbled output.
                ;; It might be a glibc-specific problem (but it can also happens
-               ;; under Mac OS X, it seems).
+               ;; under macOS, it seems).
                ;; It seems that using a pty can help circumvent the problem,
                ;; but at the cost of screwing up when the process thinks it
                ;; can ask for user input (such as password or host-key
@@ -696,7 +696,7 @@ SUBDIR is the subdirectory (if any) where this command was run.
 OLD-FIS is the list of fileinfos on which the cvs command was applied and
   which should be considered up-to-date if they are missing from the output."
   (when (eq system-type 'darwin)
-    ;; Fixup the ^D^H^H inserted at beginning of buffer sometimes on MacOSX
+    ;; Fixup the ^D^H^H inserted at beginning of buffer sometimes on macOS
     ;; because of the call to `process-send-eof'.
     (save-excursion
       (goto-char (point-min))
diff --git a/nextstep/INSTALL b/nextstep/INSTALL
index dd690abf1b1..3740346acd5 100644
--- a/nextstep/INSTALL
+++ b/nextstep/INSTALL
@@ -19,7 +19,7 @@ In the top-level directory, use:
 
   ./configure --with-ns
 
-(On Mac OS X, --with-ns is enabled by default.)
+(On macOS, --with-ns is enabled by default.)
 
 This will compile all the files, but emacs will not be able to be run except
 in -nw (terminal) mode.
diff --git a/nextstep/Makefile.in b/nextstep/Makefile.in
index 9aa034ad98d..d6e12825613 100644
--- a/nextstep/Makefile.in
+++ b/nextstep/Makefile.in
@@ -35,12 +35,12 @@ MKDIR_P = @MKDIR_P@
 
 ## Emacs.app.
 ns_appdir = @ns_appdir@
-## GNUstep: ns_appdir; OS X: ns_appdir/Contents/MacOS
+## GNUstep: ns_appdir; macOS: ns_appdir/Contents/MacOS
 ns_appbindir = @ns_appbindir@
 ## GNUstep/Emacs.base or Cocoa/Emacs.base.
 ns_appsrc = @ns_appsrc@
 ## GNUstep: GNUstep/Emacs.base/Resources/Info-gnustep.plist
-## OS X: Cocoa/Emacs.base/Contents/Info.plist
+## macOS: Cocoa/Emacs.base/Contents/Info.plist
 ns_check_file = @ns_appdir@/@ns_check_file@
 
 .PHONY: all
diff --git a/nextstep/README b/nextstep/README
index 7a1a0921cd8..6d37bb7b2d2 100644
--- a/nextstep/README
+++ b/nextstep/README
@@ -1,8 +1,8 @@
-  NS -- the Cocoa interface for OS X and compatible systems
-  ---------------------------------------------------------
+  NS -- the Cocoa interface for macOS and compatible systems
+  ----------------------------------------------------------
 
 This directory contains files needed to build Emacs on system based on
-NextStep (NS), including OS X (Mac) and GNUstep, using the Cocoa API.
+NextStep (NS), including macOS and GNUstep, using the Cocoa API.
 
 
   HISTORY
@@ -14,14 +14,14 @@ OpenStep and then Rhapsody, which became Mac OS X.  In 2004 it was
 adapted to GNUstep, a free OpenStep implementation, and in 2008 it was
 merged to the GNU Emacs trunk and released with Emacs 23.  Around the
 same time a separate Mac-only port using the Carbon APIs and
-descending from a 2001 MacOS 8/9 port of Emacs 21 was removed. (It
+descending from a 2001 Mac OS 8/9 port of Emacs 21 was removed. (It
 remains available externally under the name "mac".)
 
 
   OVERVIEW OF COCOA AND OBJECTIVE-C
 
 Cocoa is an API for the Objective-C language, an objective oriented
-superset of C.  Anybody with experience with iOS or modern OS X
+superset of C.  Anybody with experience with iOS or modern macOS
 application development should feel at home.
 
 A method call in Objective-C differs from most other languages in the
@@ -58,11 +58,11 @@ Classes are declared like the following:
 * Don't use macros and types intended for the XCode Interface Builder,
   like 'IBAction'.
 
-* The NS interface should work on all version of OS X from 10.6.8
-  (Snow Leopard) to the latest official release.
+* The NS interface should work on all version of macOS from Mac OS X
+  10.6.8 (Snow Leopard) to the latest official release.
 
-* Under OS X, it is possible to build Emacs using NS, X11, or console
-  only.  A new OS X feature should work in all appropriate builds.
+* Under macOS, it is possible to build Emacs using NS, X11, or console
+  only.  A new macOS feature should work in all appropriate builds.
 
 
   TRACING SUPPORT
@@ -76,7 +76,7 @@ uncomment the lines defining symbols starting with 'NSTRACE_GROUP'.
 
   GNUSTEP AND OTHER COMPATIBLE SYSTEMS
 
-The NS interface works on system compatible with OS X, for example
+The NS interface works on systems compatible with macOS, for example
 GNUstep.  Even though they are less frequently used, this is important
 for a number of reasons:
 
@@ -84,7 +84,7 @@ for a number of reasons:
   look-and-feel as the rest of the system.
 
 * This allows other Emacs developers to test their changes on the NS
-  interface without having access to an OS X machine.
+  interface without having access to a macOS machine.
 
 * If a feature in the NS interface work on free systems like GNUstep,
   this meets the FSF requirement that features in GNU software should
diff --git a/nextstep/templates/Emacs.desktop.in b/nextstep/templates/Emacs.desktop.in
index 170f195f270..4fed1e3b159 100644
--- a/nextstep/templates/Emacs.desktop.in
+++ b/nextstep/templates/Emacs.desktop.in
@@ -4,7 +4,7 @@ Type=Application
 Version=@version@
 Categories=GNUstep
 Name=Emacs
-Comment=GNU Emacs for NeXT/Open/GNUstep and OS X
+Comment=GNU Emacs for NeXT/Open/GNUstep and macOS
 Icon=emacs.tiff
 Exec=openapp Emacs.app
 #TryExec=Emacs.app
diff --git a/nextstep/templates/Info-gnustep.plist.in b/nextstep/templates/Info-gnustep.plist.in
index 679eb4fa435..1fd31849ab8 100644
--- a/nextstep/templates/Info-gnustep.plist.in
+++ b/nextstep/templates/Info-gnustep.plist.in
@@ -1,11 +1,11 @@
 {
-    ApplicationDescription = "GNU Emacs for GNUstep / OS X";
+    ApplicationDescription = "GNU Emacs for GNUstep / macOS";
     ApplicationIcon = emacs.tiff;
     ApplicationName = Emacs;
     ApplicationRelease = "@version@";
     Authors = (
         "Adrian Robert (GNUstep)",
-        "Christophe de Dinechin (MacOS X)",
+        "Christophe de Dinechin (macOS)",
         "Scott Bender (OpenStep)",
         "Christian Limpach (NeXTstep)",
         "Carl Edman (NeXTstep)",
diff --git a/nextstep/templates/Info.plist.in b/nextstep/templates/Info.plist.in
index dcd2fe34167..686b8047dfb 100644
--- a/nextstep/templates/Info.plist.in
+++ b/nextstep/templates/Info.plist.in
@@ -504,7 +504,7 @@ along with GNU Emacs.  If not, see <http://www.gnu.org/licenses/>.
                 </dict>
         </array>
 
-        <!-- Export definitions so that OS X understands about the file types -->
+        <!-- Export definitions so that macOS understands about the file types -->
         <key>UTExportedTypeDeclarations</key>
         <array>
                 <dict>
diff --git a/src/coding.c b/src/coding.c
index 9f709bea24c..3e4af722e4c 100644
--- a/src/coding.c
+++ b/src/coding.c
@@ -122,7 +122,7 @@ END-OF-LINE FORMAT
   How text end-of-line is encoded depends on operating system.  For
   instance, Unix's format is just one byte of LF (line-feed) code,
   whereas DOS's format is two-byte sequence of `carriage-return' and
-  `line-feed' codes.  MacOS's format is usually one byte of
+  `line-feed' codes.  Classic Mac OS's format is usually one byte of
   `carriage-return'.
 
   Since text character encoding and end-of-line encoding are
diff --git a/src/conf_post.h b/src/conf_post.h
index f83965bf8b1..d8070fad8e7 100644
--- a/src/conf_post.h
+++ b/src/conf_post.h
@@ -192,7 +192,7 @@ You lose; /* Emacs for DOS must be compiled with DJGPP */
 #endif
 #endif  /* MSDOS */
 
-/* Mac OS X / GNUstep need a bit more pure memory.  Of the existing knobs,
+/* macOS / GNUstep need a bit more pure memory.  Of the existing knobs,
    SYSTEM_PURESIZE_EXTRA seems like the least likely to cause problems.  */
 #ifdef HAVE_NS
 #if defined NS_IMPL_GNUSTEP
diff --git a/src/emacs.c b/src/emacs.c
index f8d5dfa3c6e..ce30ae741b2 100644
--- a/src/emacs.c
+++ b/src/emacs.c
@@ -2412,7 +2412,7 @@ Special values:
   `gnu'          compiled for a GNU Hurd system.
   `gnu/linux'    compiled for a GNU/Linux system.
   `gnu/kfreebsd' compiled for a GNU system with a FreeBSD kernel.
-  `darwin'       compiled for Darwin (GNU-Darwin, Mac OS X, ...).
+  `darwin'       compiled for Darwin (GNU-Darwin, macOS, ...).
   `ms-dos'       compiled as an MS-DOS application.
   `windows-nt'   compiled as a native W32 application.
   `cygwin'       compiled using the Cygwin library.
diff --git a/src/frame.c b/src/frame.c
index cfa5f7d5027..854f72e64b4 100644
--- a/src/frame.c
+++ b/src/frame.c
@@ -5088,7 +5088,7 @@ Setting this variable does not affect existing frames, only new ones.  */);
                doc: /* Default position of vertical scroll bars on this window-system.  */);
 #ifdef HAVE_WINDOW_SYSTEM
 #if defined (HAVE_NTGUI) || defined (NS_IMPL_COCOA) || (defined (USE_GTK) && defined (USE_TOOLKIT_SCROLL_BARS))
-  /* MS-Windows, Mac OS X, and GTK have scroll bars on the right by
+  /* MS-Windows, macOS, and GTK have scroll bars on the right by
      default.  */
   Vdefault_frame_scroll_bars = Qright;
 #else
diff --git a/src/gtkutil.c b/src/gtkutil.c
index 0f256c563dc..e323216bb79 100644
--- a/src/gtkutil.c
+++ b/src/gtkutil.c
@@ -2370,7 +2370,7 @@ make_widget_for_menu_item (const char *utf8_label, const char *utf8_key)
    in the group.  On exit, *GROUP contains the radio item group.
 
    Unfortunately, keys don't line up as nicely as in Motif,
-   but the MacOS X version doesn't either, so I guess that is OK.  */
+   but the macOS version doesn't either, so I guess that is OK.  */
 
 static GtkWidget *
 make_menu_item (const char *utf8_label,
diff --git a/src/macfont.h b/src/macfont.h
index 6630fb526b7..8f734527a46 100644
--- a/src/macfont.h
+++ b/src/macfont.h
@@ -1,4 +1,4 @@
-/* Interface definition for Mac OSX Core text font backend.
+/* Interface definition for macOS Core text font backend.
    Copyright (C) 2009-2016 Free Software Foundation, Inc.
 
 This file is part of GNU Emacs.
diff --git a/src/macfont.m b/src/macfont.m
index 04456283fa1..ed7c1e3bd7a 100644
--- a/src/macfont.m
+++ b/src/macfont.m
@@ -1,4 +1,4 @@
-/* Font driver on Mac OSX Core text.
+/* Font driver on macOS Core text.
    Copyright (C) 2009-2016 Free Software Foundation, Inc.
 
 This file is part of GNU Emacs.
@@ -1005,7 +1005,7 @@ macfont_set_family_cache (Lisp_Object symbol, CFStringRef string)
 and those start with ".".  NULL means the cache has been invalidated.
 Otherwise, the value is CFArray of CFStrings and the elements are
 sorted in the canonical order (CTFontManagerCompareFontFamilyNames on
-OS X 10.6 and later).  */
+Mac OS X 10.6 and later).  */
 
 static CFArrayRef macfont_available_families_cache = NULL;
 
@@ -4042,7 +4042,7 @@ mac_register_font_driver (struct frame *f)
 void
 syms_of_macfont (void)
 {
-  /* Core Text, for Mac OS X.  */
+  /* Core Text, for macOS.  */
   DEFSYM (Qmac_ct, "mac-ct");
   macfont_driver.type = Qmac_ct;
   register_font_driver (&macfont_driver, NULL);
diff --git a/src/nsfns.m b/src/nsfns.m
index 9bc6c1d3418..82bb84a147a 100644
--- a/src/nsfns.m
+++ b/src/nsfns.m
@@ -1,4 +1,4 @@
-/* Functions for the NeXT/Open/GNUstep and MacOSX window system.
+/* Functions for the NeXT/Open/GNUstep and macOS window system.
 
 Copyright (C) 1989, 1992-1994, 2005-2006, 2008-2016 Free Software
 Foundation, Inc.
@@ -22,7 +22,7 @@ along with GNU Emacs.  If not, see <http://www.gnu.org/licenses/>.  */
 Originally by Carl Edman
 Updated by Christian Limpach (chris@nice.ch)
 OpenStep/Rhapsody port by Scott Bender (sbender@harmony-ds.com)
-MacOSX/Aqua port by Christophe de Dinechin (descubes@earthlink.net)
+macOS/Aqua port by Christophe de Dinechin (descubes@earthlink.net)
 GNUstep port and post-20 update by Adrian Robert (arobert@cogsci.ucsd.edu)
 */
 
@@ -942,7 +942,7 @@ static void
 x_icon (struct frame *f, Lisp_Object parms)
 /* --------------------------------------------------------------------------
    Strangely-named function to set icon position parameters in frame.
-   This is irrelevant under OS X, but might be needed under GNUstep,
+   This is irrelevant under macOS, but might be needed under GNUstep,
    depending on the window manager used.  Note, this is not a standard
    frame parameter-setter; it is called directly from x-create-frame.
    -------------------------------------------------------------------------- */
@@ -2060,7 +2060,7 @@ DEFUN ("ns-list-services", Fns_list_services, Sns_list_services, 0, 0, 0,
 
   [svcs setAutoenablesItems: NO];
 #ifdef NS_IMPL_COCOA
-  [svcs update]; /* on OS X, converts from '/' structure */
+  [svcs update]; /* on macOS, converts from '/' structure */
 #endif
 
   ret = interpret_services_menu (svcs, Qnil, ret);
diff --git a/src/nsfont.m b/src/nsfont.m
index 92e7d1154bf..4f95ee3a1a8 100644
--- a/src/nsfont.m
+++ b/src/nsfont.m
@@ -1,4 +1,4 @@
-/* Font back-end driver for the NeXT/Open/GNUstep and MacOSX window system.
+/* Font back-end driver for the NeXT/Open/GNUstep and macOS window system.
    See font.h
    Copyright (C) 2006-2016 Free Software Foundation, Inc.
 
@@ -500,7 +500,7 @@ static NSSet
                   {
                     NSCharacterSet *fset = [[fontMgr fontWithFamily: family
                         traits: 0 weight: 5 size: 12.0] coveredCharacterSet];
-                    /* Some fonts on OS X, maybe many on GNUstep, return nil. */
+                    /* Some fonts on macOS, maybe many on GNUstep, return nil. */
                     if (fset == nil)
                       fset = [NSCharacterSet characterSetWithRange:
                                                NSMakeRange (0, 127)];
diff --git a/src/nsimage.m b/src/nsimage.m
index 5b2534b9007..66aecd4289d 100644
--- a/src/nsimage.m
+++ b/src/nsimage.m
@@ -1,4 +1,4 @@
-/* Image support for the NeXT/Open/GNUstep and MacOSX window system.
+/* Image support for the NeXT/Open/GNUstep and macOS window system.
    Copyright (C) 1989, 1992-1994, 2005-2006, 2008-2016 Free Software
    Foundation, Inc.
 
@@ -21,7 +21,7 @@ along with GNU Emacs.  If not, see <http://www.gnu.org/licenses/>.  */
 Originally by Carl Edman
 Updated by Christian Limpach (chris@nice.ch)
 OpenStep/Rhapsody port by Scott Bender (sbender@harmony-ds.com)
-MacOSX/Aqua port by Christophe de Dinechin (descubes@earthlink.net)
+macOS/Aqua port by Christophe de Dinechin (descubes@earthlink.net)
 GNUstep port and post-20 update by Adrian Robert (arobert@cogsci.ucsd.edu)
 */
 
diff --git a/src/nsmenu.m b/src/nsmenu.m
index 7d340e8ec83..f73c184dce7 100644
--- a/src/nsmenu.m
+++ b/src/nsmenu.m
@@ -1,4 +1,4 @@
-/* NeXT/Open/GNUstep and MacOSX Cocoa menu and toolbar module.
+/* NeXT/Open/GNUstep and macOS Cocoa menu and toolbar module.
    Copyright (C) 2007-2016 Free Software Foundation, Inc.
 
 This file is part of GNU Emacs.
@@ -93,7 +93,7 @@ popup_activated (void)
 /* --------------------------------------------------------------------------
     Update menubar.  Three cases:
     1) ! deep_p, submenu = nil: Fresh switch onto a frame -- either set up
-       just top-level menu strings (OS X), or goto case (2) (GNUstep).
+       just top-level menu strings (macOS), or goto case (2) (GNUstep).
     2) deep_p, submenu = nil: Recompute all submenus.
     3) deep_p, submenu = non-nil: Update contents of a single submenu.
    -------------------------------------------------------------------------- */
@@ -584,7 +584,7 @@ x_activate_menubar (struct frame *f)
     return;
 /*fprintf (stderr, "Updating menu '%s'\n", [[self title] UTF8String]); NSLog (@"%@\n", event); */
 #ifdef NS_IMPL_GNUSTEP
-  /* Don't know how to do this for anything other than OSX >= 10.5
+  /* Don't know how to do this for anything other than Mac OS X 10.5 and later.
      This is wrong, as it might run Lisp code in the event loop.  */
   ns_update_menubar (frame, true, self);
 #endif
@@ -645,7 +645,7 @@ x_activate_menubar (struct frame *f)
 
       keyEq = [self parseKeyEquiv: wv->key];
 #ifdef NS_IMPL_COCOA
-      /* OS X just ignores modifier strings longer than one character */
+      /* macOS just ignores modifier strings longer than one character */
       if (keyEquivModMask == 0)
         title = [title stringByAppendingFormat: @" (%@)", keyEq];
 #endif
@@ -1057,9 +1057,9 @@ update_frame_tool_bar (struct frame *f)
       /* Check if this is a separator.  */
       if (EQ (TOOLPROP (TOOL_BAR_ITEM_TYPE), Qt))
         {
-          /* Skip separators.  Newer OSX don't show them, and on GNUstep they
-             are wide as a button, thus overflowing the toolbar most of
-             the time.  */
+          /* Skip separators.  Newer macOS don't show them, and on
+             GNUstep they are wide as a button, thus overflowing the
+             toolbar most of the time.  */
           continue;
         }
 
diff --git a/src/nsselect.m b/src/nsselect.m
index eba23932e65..b7c9148ee05 100644
--- a/src/nsselect.m
+++ b/src/nsselect.m
@@ -1,4 +1,4 @@
-/* NeXT/Open/GNUstep / MacOSX Cocoa selection processing for emacs.
+/* NeXT/Open/GNUstep / macOS Cocoa selection processing for emacs.
    Copyright (C) 1993-1994, 2005-2006, 2008-2016 Free Software
    Foundation, Inc.
 
@@ -21,7 +21,7 @@ along with GNU Emacs.  If not, see <http://www.gnu.org/licenses/>.  */
 Originally by Carl Edman
 Updated by Christian Limpach (chris@nice.ch)
 OpenStep/Rhapsody port by Scott Bender (sbender@harmony-ds.com)
-MacOSX/Aqua port by Christophe de Dinechin (descubes@earthlink.net)
+macOS/Aqua port by Christophe de Dinechin (descubes@earthlink.net)
 GNUstep port and post-20 update by Adrian Robert (arobert@cogsci.ucsd.edu)
 */
 
diff --git a/src/nsterm.m b/src/nsterm.m
index 4d9d10559ea..4f99a13c44e 100644
--- a/src/nsterm.m
+++ b/src/nsterm.m
@@ -1,4 +1,4 @@
-/* NeXT/Open/GNUstep / MacOSX communication module.      -*- coding: utf-8 -*-
+/* NeXT/Open/GNUstep / macOS communication module.      -*- coding: utf-8 -*-
 
 Copyright (C) 1989, 1993-1994, 2005-2006, 2008-2016 Free Software
 Foundation, Inc.
@@ -22,7 +22,7 @@ along with GNU Emacs.  If not, see <http://www.gnu.org/licenses/>.  */
 Originally by Carl Edman
 Updated by Christian Limpach (chris@nice.ch)
 OpenStep/Rhapsody port by Scott Bender (sbender@harmony-ds.com)
-MacOSX/Aqua port by Christophe de Dinechin (descubes@earthlink.net)
+macOS/Aqua port by Christophe de Dinechin (descubes@earthlink.net)
 GNUstep port and post-20 update by Adrian Robert (arobert@cogsci.ucsd.edu)
 */
 
@@ -250,7 +250,7 @@ static unsigned convert_ns_to_X_keysym[] =
   0x1B,                         0x1B   /* escape */
 };
 
-/* On OS X picks up the default NSGlobalDomain AppleAntiAliasingThreshold,
+/* On macOS picks up the default NSGlobalDomain AppleAntiAliasingThreshold,
    the maximum font size to NOT antialias.  On GNUstep there is currently
    no way to control this behavior. */
 float ns_antialias_threshold;
@@ -587,7 +587,7 @@ ns_load_path (void)
 
 void
 ns_init_locale (void)
-/* OS X doesn't set any environment variables for the locale when run
+/* macOS doesn't set any environment variables for the locale when run
    from the GUI. Get the locale from the OS and set LANG. */
 {
   NSLocale *locale = [NSLocale currentLocale];
@@ -596,7 +596,7 @@ ns_init_locale (void)
 
   @try
     {
-      /* It seems OS X should probably use UTF-8 everywhere.
+      /* It seems macOS should probably use UTF-8 everywhere.
          'localeIdentifier' does not specify the encoding, and I can't
          find any way to get the OS to tell us which encoding to use,
          so hard-code '.UTF-8'. */
@@ -718,7 +718,7 @@ ns_screen_margins (NSScreen *screen)
 
 
 /* A screen margin between 1 and DOCK_IGNORE_LIMIT (inclusive) is
-   assumed to contain a hidden dock.  OS X currently use 4 pixels for
+   assumed to contain a hidden dock.  macOS currently use 4 pixels for
    this, however, to be future compatible, a larger value is used.  */
 #define DOCK_IGNORE_LIMIT 6
 
@@ -731,7 +731,7 @@ reserved for an hidden dock.  */
 
   struct EmacsMargins margins = ns_screen_margins(screen);
 
-  /* OS X (currently) reserved 4 pixels along the edge where a hidden
+  /* macOS (currently) reserved 4 pixels along the edge where a hidden
      dock is located.  Unfortunately, it's not possible to find the
      location and information about if the dock is hidden.  Instead,
      it is assumed that if the margin of an edge is less than
@@ -748,7 +748,7 @@ reserved for an hidden dock.  */
     {
       margins.top = 0;
     }
-  /* Note: This doesn't occur in current versions of OS X, but
+  /* Note: This doesn't occur in current versions of macOS, but
      included for completeness and future compatibility.  */
   if (margins.bottom <= DOCK_IGNORE_LIMIT)
     {
@@ -1027,7 +1027,7 @@ ns_update_begin (struct frame *f)
 #ifdef NS_IMPL_COCOA
   if ([view isFullscreen] && [view fsIsNative])
   {
-    // Fix reappearing tool bar in fullscreen for OSX 10.7
+    // Fix reappearing tool bar in fullscreen for Mac OS X 10.7
     BOOL tbar_visible = FRAME_EXTERNAL_TOOL_BAR (f) ? YES : NO;
     NSToolbar *toolbar = [FRAME_NS_VIEW (f) toolbar];
     if (! tbar_visible != ! [toolbar isVisible])
@@ -1986,8 +1986,8 @@ ns_get_color (const char *name, NSColor **col)
     }
   else if ([nsname isEqualToString: @"ns_selection_fg_color"])
     {
-      /* NOTE: OSX applications normally don't set foreground selection, but
-         text may be unreadable if we don't.
+      /* NOTE: macOS applications normally don't set foreground
+         selection, but text may be unreadable if we don't.
       */
       if ((new = [NSColor selectedTextColor]) != nil)
         {
@@ -3937,7 +3937,7 @@ ns_send_appdefined (int value)
 #ifdef NS_IMPL_COCOA
   if (! send_appdefined)
     {
-      /* OSX 10.10.1 swallows the AppDefined event we are sending ourselves
+      /* OS X 10.10.1 swallows the AppDefined event we are sending ourselves
          in certain situations (rapid incoming events).
          So check if we have one, if not add one.  */
       NSEvent *appev = [NSApp nextEventMatchingMask:NSApplicationDefinedMask
@@ -4816,7 +4816,7 @@ ns_term_init (Lisp_Object display_name)
   [outerpool release];
   outerpool = [[NSAutoreleasePool alloc] init];
 
-  /* count object allocs (About, click icon); on OS X use ObjectAlloc tool */
+  /* count object allocs (About, click icon); on macOS use ObjectAlloc tool */
   /*GSDebugAllocationActive (YES); */
   block_input ();
 
@@ -4945,7 +4945,7 @@ ns_term_init (Lisp_Object display_name)
 
   ns_app_name = [[NSProcessInfo processInfo] processName];
 
-  /* Set up OS X app menu */
+  /* Set up macOS app menu */
 
   NSTRACE_MSG ("Menu init");
 
@@ -5017,7 +5017,7 @@ ns_term_init (Lisp_Object display_name)
          selector: @selector (trackingNotification:)
              name: NSMenuDidEndTrackingNotification object: mainMenu];
   }
-#endif /* MAC OS X menu setup */
+#endif /* macOS menu setup */
 
   /* Register our external input/output types, used for determining
      applicable services and also drag/drop eligibility. */
@@ -5245,7 +5245,7 @@ ns_term_shutdown (int sig)
 
 #ifdef NS_IMPL_COCOA
   /* If no dialog and none of our frames have focus and it is a move, skip it.
-     It is a mouse move in an auxiliary menu, i.e. on the top right on OSX,
+     It is a mouse move in an auxiliary menu, i.e. on the top right on macOS,
      such as Wifi, sound, date or similar.
      This prevents "spooky" highlighting in the frame under the menu.  */
   if (type == NSMouseMoved && [NSApp modalWindow] == nil)
@@ -5784,7 +5784,7 @@ not_in_argv (NSString *arg)
 
   NSTRACE ("[EmacsView keyDown:]");
 
-  /* Rhapsody and OS X give up and down events for the arrow keys */
+  /* Rhapsody and macOS give up and down events for the arrow keys */
   if (ns_fake_keydown == YES)
     ns_fake_keydown = NO;
   else if ([theEvent type] != NSKeyDown)
@@ -6018,7 +6018,7 @@ not_in_argv (NSString *arg)
 
 
 #ifdef NS_IMPL_COCOA
-/* Needed to pick up Ctrl-tab and possibly other events that OS X has
+/* Needed to pick up Ctrl-tab and possibly other events that Mac OS X
    decided not to send key-down for.
    See http://osdir.com/ml/editors.vim.mac/2007-10/msg00141.html
    This only applies on Tiger and earlier.
@@ -7176,8 +7176,8 @@ not_in_argv (NSString *arg)
 #if MAC_OS_X_VERSION_MAX_ALLOWED >= MAC_OS_X_VERSION_10_7
       unsigned val = (unsigned)[NSApp presentationOptions];
 
-      // OSX 10.7 bug fix, the menu won't appear without this.
-      // val is non-zero on other OSX versions.
+      // Mac OS X 10.7 bug fix, the menu won't appear without this.
+      // val is non-zero on other macOS versions.
       if (val == 0)
         {
           NSApplicationPresentationOptions options
@@ -7601,7 +7601,7 @@ not_in_argv (NSString *arg)
   unblock_input ();
 
   /*
-    drawRect: may be called (at least in OS X 10.5) for invisible
+    drawRect: may be called (at least in Mac OS X 10.5) for invisible
     views as well for some reason.  Thus, do not infer visibility
     here.
 
@@ -8123,7 +8123,7 @@ not_in_argv (NSString *arg)
   [self setEnabled: YES];
 
   /* Ensure auto resizing of scrollbars occurs within the emacs frame's view
-     locked against the top and bottom edges, and right edge on OS X, where
+     locked against the top and bottom edges, and right edge on macOS, where
      scrollers are on right. */
 #ifdef NS_IMPL_GNUSTEP
   [self setAutoresizingMask: NSViewMaxXMargin | NSViewHeightSizable];
@@ -8730,14 +8730,14 @@ allowing it to be used at a lower level for accented character entry.");
 
   DEFVAR_LISP ("ns-auto-hide-menu-bar", ns_auto_hide_menu_bar,
                doc: /* Non-nil means that the menu bar is hidden, but appears when the mouse is near.
-Only works on OSX 10.6 or later.  */);
+Only works on Mac OS X 10.6 or later.  */);
   ns_auto_hide_menu_bar = Qnil;
 
   DEFVAR_BOOL ("ns-use-native-fullscreen", ns_use_native_fullscreen,
-     doc: /*Non-nil means to use native fullscreen on OSX >= 10.7.
+     doc: /*Non-nil means to use native fullscreen on Mac OS X 10.7 and later.
 Nil means use fullscreen the old (< 10.7) way.  The old way works better with
-multiple monitors, but lacks tool bar.  This variable is ignored on OSX < 10.7.
-Default is t for OSX >= 10.7, nil otherwise.  */);
+multiple monitors, but lacks tool bar.  This variable is ignored on
+Mac OS X < 10.7.  Default is t for 10.7 and later, nil otherwise.  */);
 #ifdef HAVE_NATIVE_FS
   ns_use_native_fullscreen = YES;
 #else
@@ -8752,9 +8752,9 @@ Default is nil.  */);
   ns_use_fullscreen_animation = NO;
 
   DEFVAR_BOOL ("ns-use-srgb-colorspace", ns_use_srgb_colorspace,
-     doc: /*Non-nil means to use sRGB colorspace on OSX >= 10.7.
+     doc: /*Non-nil means to use sRGB colorspace on Mac OS X 10.7 and later.
 Note that this does not apply to images.
-This variable is ignored on OSX < 10.7 and GNUstep.  */);
+This variable is ignored on Mac OS X < 10.7 and GNUstep.  */);
   ns_use_srgb_colorspace = YES;
 
   /* TODO: move to common code */
diff --git a/src/sysdep.c b/src/sysdep.c
index 460166d119e..674e76db7a0 100644
--- a/src/sysdep.c
+++ b/src/sysdep.c
@@ -2337,7 +2337,7 @@ posix_close (int fd, int flag)
      closed, and retrying the close could inadvertently close a file
      descriptor allocated by some other thread.  In other systems
      (e.g., HP/UX) FD is not closed.  And in still other systems
-     (e.g., OS X, Solaris), maybe FD is closed, maybe not, and in a
+     (e.g., macOS, Solaris), maybe FD is closed, maybe not, and in a
      multithreaded program there can be no way to tell.
 
      So, in this case, pretend that the close succeeded.  This works
diff --git a/src/unexmacosx.c b/src/unexmacosx.c
index bdacc8b540b..f755f7fafd9 100644
--- a/src/unexmacosx.c
+++ b/src/unexmacosx.c
@@ -1,4 +1,4 @@
-/* Dump Emacs in Mach-O format for use on Mac OS X.
+/* Dump Emacs in Mach-O format for use on macOS.
    Copyright (C) 2001-2016 Free Software Foundation, Inc.
 
 This file is part of GNU Emacs.
@@ -24,7 +24,7 @@ along with GNU Emacs.  If not, see <http://www.gnu.org/licenses/>.  */
    Mach-O format: the file loader.h, man pages for Mach-O and ld, old
    NEXTSTEP documents of the Mach-O format.  The tool otool dumps the
    mach header (-h option) and the load commands (-l option) in a
-   Mach-O file.  The tool nm on Mac OS X displays the symbol table in
+   Mach-O file.  The tool nm on macOS displays the symbol table in
    a Mach-O file.  For examples of unexec for the Mach-O format, see
    the file unexnext.c in the GNU Emacs distribution, the file
    unexdyld.c in the Darwin port of GNU Emacs 20.7, and unexdyld.c in
@@ -33,7 +33,7 @@ along with GNU Emacs.  If not, see <http://www.gnu.org/licenses/>.  */
    Read that to see what they do.  This file was written completely
    from scratch, making use of information from the above sources.  */
 
-/* The Mac OS X implementation of unexec makes use of Darwin's `zone'
+/* The macOS implementation of unexec makes use of Darwin's `zone'
    memory allocator.  All calls to malloc, realloc, and free in Emacs
    are redirected to unexec_malloc, unexec_realloc, and unexec_free in
    this file.  When temacs is run, all memory requests are handled in
@@ -49,7 +49,7 @@ along with GNU Emacs.  If not, see <http://www.gnu.org/licenses/>.  */
    block must be obtained by malloc and the old contents copied to
    it.  */
 
-/* Peculiarity of the Mach-O files generated by ld in Mac OS X
+/* Peculiarity of the Mach-O files generated by ld in macOS
    (possible causes of future bugs if changed).
 
    The file offset of the start of the __TEXT segment is zero.  Since
@@ -118,9 +118,9 @@ along with GNU Emacs.  If not, see <http://www.gnu.org/licenses/>.  */
 
 #include <assert.h>
 
-/* LC_DATA_IN_CODE is not defined in mach-o/loader.h on OS X 10.7.
+/* LC_DATA_IN_CODE is not defined in mach-o/loader.h on Mac OS X 10.7.
    But it is used if we build with "Command Line Tools for Xcode 4.5
-   (OS X Lion) - September 2012".  */
+   (Mac OS X Lion) - September 2012".  */
 #ifndef LC_DATA_IN_CODE
 #define LC_DATA_IN_CODE 0x29 /* table of non-instructions in __text */
 #endif