diff --git a/lib/libsys/open.2 b/lib/libsys/open.2
--- a/lib/libsys/open.2
+++ b/lib/libsys/open.2
@@ -137,46 +137,97 @@
 .Dv vfs.lookup_cap_dotdot_nonlocal
 MIB is set to zero, ".." is not allowed if found on non-local filesystem.
 .Pp
-The flags specified are formed by
+The
+.Fa flags
+are formed by
 .Em or Ns 'ing
-the following values
+the following values:
 .Pp
-.Bd -literal -offset indent -compact
-O_RDONLY	open for reading only
-O_WRONLY	open for writing only
-O_RDWR		open for reading and writing
-O_EXEC		open for execute only
-O_SEARCH	open for search only, an alias for O_EXEC
-O_NONBLOCK	do not block on open
-O_APPEND	append on each write
-O_CREAT		create file if it does not exist
-O_TRUNC		truncate size to 0
-O_EXCL		error if create and file exists
-O_SHLOCK	atomically obtain a shared lock
-O_EXLOCK	atomically obtain an exclusive lock
-O_DIRECT	eliminate or reduce cache effects
-O_FSYNC		synchronous writes (historical synonym for O_SYNC)
-O_SYNC		synchronous writes
-O_DSYNC		synchronous data writes
-O_NOFOLLOW	do not follow symlinks
-O_NOCTTY	ignored
-O_TTY_INIT	ignored
-O_DIRECTORY	error if file is not a directory
-O_CLOEXEC	set FD_CLOEXEC upon open
-O_VERIFY	verify the contents of the file
-O_RESOLVE_BENEATH	path resolution must not cross the fd directory
-O_PATH		record only the target path in the opened descriptor
-O_EMPTY_PATH	openat, open file referenced by fd if path is empty
-.Ed
+.Bl -tag -width O_RESOLVE_BENEATH
+.It Dv O_RDONLY
+open for reading only
+.It Dv O_WRONLY
+open for writing only
+.It Dv O_RDWR
+open for reading and writing
+.It Dv O_EXEC
+open for execute only
+.It Dv O_SEARCH
+open for search only
+(an alias for
+.Dv O_EXEC
+typically used with
+.Dv O_DIRECTORY )
+.It Dv O_NONBLOCK
+do not block on open
+.It Dv O_APPEND
+append on each write instead of writing at the current file pointer
+.It Dv O_CREAT
+create file if it does not exist
+.It Dv O_TRUNC
+truncate size to 0
+.It Dv O_EXCL
+fail if
+.Dv O_CREAT
+is set and the file exists
+.It Dv O_SHLOCK
+atomically obtain a shared lock
+.It Dv O_EXLOCK
+atomically obtain an exclusive lock
+.It Dv O_DIRECT
+eliminate or reduce effects of data caching
+.It Dv O_FSYNC
+synchronous data and metadata writes
+.Pq historical synonym for Dv O_SYNC
+.It Dv O_SYNC
+synchronous data and metadata writes
+.It Dv O_DSYNC
+synchronous data writes
+.It Dv O_NOFOLLOW
+do not follow symlinks
+.It Dv O_NOCTTY
+ignored
+.It Dv O_TTY_INIT
+ignored
+.It Dv O_DIRECTORY
+error if file is not a directory
+.It Dv O_CLOEXEC
+automatically close file on
+.Xr execve 2
+.It Dv O_VERIFY
+verify the contents of the file
+.It Dv O_RESOLVE_BENEATH
+.Pq Xr openat 2 only
+path resolution must not cross the
+.Fa fd
+directory
+.It Dv O_PATH
+record only the target path in the opened descriptor
+.It Dv O_EMPTY_PATH
+.Pq Xr openat 2 only
+open file referenced by
+.Fa fd
+if path is empty
+.El
+.Pp
+Exactly one of the flags
+.Dv O_RDONLY ,
+.Dv O_WRONLY ,
+.Dv O_RDWR ,
+or
+.Dv O_EXEC
+must be provided.
 .Pp
 Opening a file with
 .Dv O_APPEND
 set causes each write on the file
 to be appended to the end.
+.Pp
 If
 .Dv O_TRUNC
 is specified and the
 file exists, the file is truncated to zero length.
+.Pp
 If
 .Dv O_EXCL
 is set with
@@ -184,7 +235,8 @@
 and the file already
 exists,
 .Fn open
-returns an error.
+fails with
+.Er EEXIST .
 This may be used to
 implement a simple exclusive access locking mechanism.
 If
@@ -194,12 +246,13 @@
 .Fn open
 will fail even if the symbolic
 link points to a non-existent name.
-If the
+.Pp
+If
 .Dv O_NONBLOCK
-flag is specified and the
+is specified and the
 .Fn open
-system call would result
-in the process being blocked for some reason (e.g., waiting for
+system call would
+block for some reason (for example, waiting for
 carrier on a dialup line),
 .Fn open
 returns immediately.
@@ -302,16 +355,14 @@
 Absolute paths or even the temporal escape from beneath of the starting
 directory is not allowed.
 .Pp
-When
-.Fa fd
+When a directory
 is opened with
 .Dv O_SEARCH ,
 execute permissions are checked at open time.
-The
-.Fa fd
+The returned file descriptor
 may not be used for any read operations like
 .Xr getdirentries 2 .
-The primary use for this descriptor will be as the lookup descriptor for the
+The primary use of this descriptor is as the lookup descriptor for the
 .Fn *at
 family of functions.
 If
@@ -319,7 +370,9 @@
 was not requested at open time, then the
 .Fn *at
 functions use the current directory permissions for the directory referenced
-by the descriptor at the time of the call.
+by the descriptor at the time of the
+.Fn *at
+call.
 .Pp
 .Dv O_PATH
 returns a file descriptor that can be used as a directory file descriptor for
@@ -328,9 +381,9 @@
 .Xr fstatat 2
 and others.
 The other functionality of the returned file descriptor is limited to
-the descriptor-level operations.
-It can be used for
-.Bl -tag -width readlinkat(2) -offset indent -compact
+the following descriptor-level operations:
+.Pp
+.Bl -tag -width __acl_aclcheck_fd -offset indent -compact
 .It Xr fcntl 2
 but advisory locking is not allowed
 .It Xr dup 2
@@ -344,12 +397,14 @@
 .Dv SCM_RIGHTS
 message
 .It Xr kqueue 2
-using for
+only with
 .Dv EVFILT_VNODE
 .It Xr readlinkat 2
-.It Xr __acl_get_fd 2 , Xr __acl_aclcheck_fd 2
+.It Xr __acl_get_fd 2
+.It Xr __acl_aclcheck_fd 2
 .El
-But operations like
+.Pp
+Other operations like
 .Xr read 2 ,
 .Xr ftruncate 2 ,
 and any other that operate on file and not on file descriptor (except
@@ -358,18 +413,19 @@
 .Pp
 A file descriptor created with the
 .Dv O_PATH
-flag can be opened into normal (operable) file descriptor by
+flag can be opened as a normal (operable) file descriptor by
 specifying it as the
 .Fa fd
 argument to
 .Fn openat
-with empty
+with an empty
 .Fa path
-and flag
-.Dv O_EMPTY_PATH .
+and the
+.Dv O_EMPTY_PATH
+flag.
 Such an open behaves as if the current path of the file referenced by
 .Fa fd
-is passed, except that the path walk permissions are not checked.
+is passed, except that path walk permissions are not checked.
 See also the description of
 .Dv AT_EMPTY_PATH
 flag for
@@ -394,7 +450,7 @@
 .Xr mkfifo 2 )
 is restarted as normal.
 .Pp
-When a new file is created it is given the group of the directory
+When a new file is created, it is assigned the group of the directory
 which contains it.
 .Pp
 Unless
@@ -405,9 +461,9 @@
 system calls; see
 .Xr close 2 ,
 .Xr fcntl 2
-and
+and the description of the
 .Dv O_CLOEXEC
-description.
+flag.
 .Pp
 The system imposes a limit on the number of file descriptors
 open simultaneously by one process.
@@ -511,7 +567,7 @@
 is specified but the underlying file system does not support locking.
 .It Bq Er EOPNOTSUPP
 The named file is a special file mounted through a file system that
-does not support access to it (e.g.\& NFS).
+does not support access to it (for example, NFS).
 .It Bq Er EWOULDBLOCK
 .Dv O_NONBLOCK
 and one of
@@ -688,7 +744,7 @@
 .\" .St -p1003.1-2017 ,
 .\" XXX: This should be replaced in the future when an appropriate argument to
 .\" the St macro is available: -p1003.1-2017
-.No IEEE Std 1003.1-2008, 2017 Edition (\\(LqPOSIX.1\\(Rq) ,
+.No IEEE Std 1003.1-2008, 2017 Edition ("POSIX.1") ,
 which specifies that behavior for
 .Dv O_SEARCH ,
 in the absence of the flag the implementation checks the current