Replace `iff' in comments.

40 files changed, 60 insertions, 60 deletions

diff --git a/src/buffer.h b/src/buffer.h
index 65cfef4f04f..ed99dc4ffb1 100644
--- a/src/buffer.h
+++ b/src/buffer.h
@@ -561,7 +561,7 @@ struct buffer
   Lisp_Object filename;
   /* Dir for expanding relative file names.  */
   Lisp_Object directory;
-  /* True iff this buffer has been backed up (if you write to the
+  /* True if this buffer has been backed up (if you write to the
      visited file and it hasn't been backed up, then a backup will
      be made).  */
   /* This isn't really used by the C code, so could be deleted.  */
diff --git a/src/callproc.c b/src/callproc.c
index 1ea0dfa43a6..bf7ea43b868 100644
--- a/src/callproc.c
+++ b/src/callproc.c
@@ -117,7 +117,7 @@ Lisp_Object Vprocess_environment;
 Lisp_Object Qbuffer_file_type;
 #endif /* DOS_NT */
 
-/* True iff we are about to fork off a synchronous process or if we
+/* True if we are about to fork off a synchronous process or if we
    are waiting for it.  */
 int synch_process_alive;
 
diff --git a/src/casetab.c b/src/casetab.c
index 1d364a6df7e..a53bb1ece52 100644
--- a/src/casetab.c
+++ b/src/casetab.c
@@ -40,7 +40,7 @@ static void set_identity ();
 static void shuffle ();
 
 DEFUN ("case-table-p", Fcase_table_p, Scase_table_p, 1, 1, 0,
-       doc: /* Return t iff OBJECT is a case table.
+       doc: /* Return t if OBJECT is a case table.
 See `set-case-table' for more information on these data structures.  */)
      (object)
      Lisp_Object object;
diff --git a/src/category.c b/src/category.c
index 55e752045e7..7ea9b7810fa 100644
--- a/src/category.c
+++ b/src/category.c
@@ -559,7 +559,7 @@ syms_of_category ()
 	       doc: /* List of pair (cons) of categories to determine word boundary.
 
 Emacs treats a sequence of word constituent characters as a single
-word (i.e. finds no word boundary between them) iff they belongs to
+word (i.e. finds no word boundary between them) only if they belong to
 the same charset.  But, exceptions are allowed in the following cases.
 
 \(1) The case that characters are in different charsets is controlled
diff --git a/src/ccl.c b/src/ccl.c
index c25e67abf57..564fd4ba4fa 100644
--- a/src/ccl.c
+++ b/src/ccl.c
@@ -659,13 +659,13 @@ while (0)
 
 #define CCL_LookupIntConstTbl 0x13 /* Lookup multibyte character by
 				      integer key.  Afterwards R7 set
-				      to 1 iff lookup succeeded.
+				      to 1 if lookup succeeded.
 				      1:ExtendedCOMMNDRrrRRRXXXXXXXX
 				      2:ARGUMENT(Hash table ID) */
 
 #define CCL_LookupCharConstTbl 0x14 /* Lookup integer by multibyte
 				       character key.  Afterwards R7 set
-				       to 1 iff lookup succeeded.
+				       to 1 if lookup succeeded.
 				       1:ExtendedCOMMNDRrrRRRrrrXXXXX
 				       2:ARGUMENT(Hash table ID) */
 
diff --git a/src/charset.c b/src/charset.c
index a6ec309cbb3..1a85cd39c72 100644
--- a/src/charset.c
+++ b/src/charset.c
@@ -337,7 +337,7 @@ split_string (str, len, charset, c1, c2)
   return 0;
 }
 
-/* Return 1 iff character C has valid printable glyph.
+/* Return 1 if character C has valid printable glyph.
    Use the macro CHAR_PRINTABLE_P instead.  */
 int
 char_printable_p (c)
@@ -1102,8 +1102,8 @@ DIMENSION, CHARS, and FINAL-CHAR.  */)
   return CHARSET_SYMBOL (charset);
 }
 
-/* If GENERICP is nonzero, return nonzero iff C is a valid normal or
-   generic character.  If GENERICP is zero, return nonzero iff C is a
+/* If GENERICP is nonzero, return nonzero if C is a valid normal or
+   generic character.  If GENERICP is zero, return nonzero if C is a
    valid normal character.  Do not call this function directly,
    instead use macro CHAR_VALID_P.  */
 int
diff --git a/src/charset.h b/src/charset.h
index 984d466d97d..c20766f910b 100644
--- a/src/charset.h
+++ b/src/charset.h
@@ -413,8 +413,8 @@ extern int width_by_char_head[256];
 	    | ((c1) <= 0 ? 0 : (((c1) & 0x7F) << 7))))))
 
 
-/* If GENERICP is nonzero, return nonzero iff C is a valid normal or
-   generic character.  If GENERICP is zero, return nonzero iff C is a
+/* If GENERICP is nonzero, return nonzero if C is a valid normal or
+   generic character.  If GENERICP is zero, return nonzero if C is a
    valid normal character.  */
 #define CHAR_VALID_P(c, genericp)	\
   ((c) >= 0				\
@@ -450,7 +450,7 @@ extern int width_by_char_head[256];
 #define VALID_LEADING_CODE_P(code)	\
   (! NILP (CHARSET_TABLE_ENTRY (code)))
 
-/* Return 1 iff the byte sequence at unibyte string STR (LENGTH bytes)
+/* Return 1 if the byte sequence at unibyte string STR (LENGTH bytes)
    is valid as a multibyte form.  If valid, by a side effect, BYTES is
    set to the byte length of the multibyte form.  */
 
@@ -471,7 +471,7 @@ extern int width_by_char_head[256];
 		     && VALID_LEADING_CODE_P (str[1]))))))))
 
 
-/* Return 1 iff the byte sequence at multibyte string STR is valid as
+/* Return 1 if the byte sequence at multibyte string STR is valid as
    a unibyte form.  By a side effect, BYTES is set to the byte length
    of one character at STR.  */
 
@@ -499,7 +499,7 @@ extern int width_by_char_head[256];
 	 c1 = CHAR_FIELD3 (c),						    \
 	 c2 = -1)))
 
-/* Return 1 iff character C has valid printable glyph.  */
+/* Return 1 if character C has valid printable glyph.  */
 #define CHAR_PRINTABLE_P(c) (ASCII_BYTE_P (c) || char_printable_p (c))
 
 /* The charset of the character at STR is stored in CHARSET, and the
diff --git a/src/coding.h b/src/coding.h
index 9906e66af6c..2efcd4f47e2 100644
--- a/src/coding.h
+++ b/src/coding.h
@@ -263,7 +263,7 @@ enum coding_type
 				     eol-type is not consistent
 				     through the file.  */
 
-/* 1 iff composing.  */
+/* 1 if composing.  */
 #define COMPOSING_P(coding) ((int) coding->composing > (int) COMPOSITION_NO)
 
 #define COMPOSITION_DATA_SIZE 4080
@@ -372,7 +372,7 @@ struct coding_system
   /* The current status of composition handling.  */
   int composing;
 
-  /* 1 iff the next character is a composition rule.  */
+  /* 1 if the next character is a composition rule.  */
   int composition_rule_follows;
 
   /* Information of compositions are stored here on decoding and set
diff --git a/src/composite.h b/src/composite.h
index 5dc8dde62e2..ba8f8c84104 100644
--- a/src/composite.h
+++ b/src/composite.h
@@ -56,7 +56,7 @@ enum composition_method {
 /* Temporary variable used only in the following macros.  */
 extern Lisp_Object composition_temp;
 
-/* Return 1 iff the composition is already registered.  */
+/* Return 1 if the composition is already registered.  */
 #define COMPOSITION_REGISTERD_P(prop) INTEGERP (XCAR (prop))
 
 /* Return ID number of the already registered composition.  */
@@ -91,7 +91,7 @@ extern Lisp_Object composition_temp;
 	  ? COMPOSITION_WITH_ALTCHARS					\
 	  : COMPOSITION_WITH_RULE_ALTCHARS))))
 
-/* Return 1 iff the composition is valid.  It is valid if length of
+/* Return 1 if the composition is valid.  It is valid if length of
    the composition equals to (END - START).  */
 #define COMPOSITION_VALID_P(start, end, prop)			\
   (CONSP (prop)							\
diff --git a/src/dired.c b/src/dired.c
index 22283b66ea0..1fb5387268a 100644
--- a/src/dired.c
+++ b/src/dired.c
@@ -916,7 +916,7 @@ Elements of the attribute list are:
  7. Size in bytes.
   This is a floating point number if the size is too large for an integer.
  8. File modes, as a string of ten letters or dashes as in ls -l.
- 9. t iff file's gid would change if file were deleted and recreated.
+ 9. t if file's gid would change if file were deleted and recreated.
 10. inode number.  If inode number is larger than the Emacs integer,
   this is a cons cell containing two integers: first the high part,
   then the low 16 bits.
diff --git a/src/editfns.c b/src/editfns.c
index 5ab8e5eddc8..6c6742d242e 100644
--- a/src/editfns.c
+++ b/src/editfns.c
@@ -3516,7 +3516,7 @@ usage: (format STRING &rest OBJECTS)  */)
 	   precision	::= '.' [0-9]*
 
 	   If a field-width is specified, it specifies to which width
-	   the output should be padded with blanks, iff the output
+	   the output should be padded with blanks, if the output
 	   string is shorter than field-width.
 
 	   If precision is specified, it specifies the number of
diff --git a/src/eval.c b/src/eval.c
index 60e3c77a3a3..026a3375589 100644
--- a/src/eval.c
+++ b/src/eval.c
@@ -1785,7 +1785,7 @@ signal_error (s, arg)
 }
 
 
-/* Return nonzero iff LIST is a non-nil atom or
+/* Return nonzero if LIST is a non-nil atom or
    a list containing one of CONDITIONS.  */
 
 static int
diff --git a/src/fileio.c b/src/fileio.c
index 1962035e0bd..26723fa4f3e 100644
--- a/src/fileio.c
+++ b/src/fileio.c
@@ -5191,7 +5191,7 @@ This does code conversion according to the value of
  * if we do writes that don't end with a carriage return. Furthermore
  * it cannot handle writes of more then 16K. The modified
  * version of "sys_write" in SYSDEP.C (see comment there) copes with
- * this EXCEPT for the last record (iff it doesn't end with a carriage
+ * this EXCEPT for the last record (if it doesn't end with a carriage
  * return). This implies that if your buffer doesn't end with a carriage
  * return, you get one free... tough. However it also means that if
  * we make two calls to sys_write (a la the following code) you can
diff --git a/src/fontset.c b/src/fontset.c
index bf6f7121b23..b670e228047 100644
--- a/src/fontset.c
+++ b/src/fontset.c
@@ -500,7 +500,7 @@ free_face_fontset (f, face)
 }
 
 
-/* Return 1 iff FACE is suitable for displaying character C.
+/* Return 1 if FACE is suitable for displaying character C.
    Otherwise return 0.  Called from the macro FACE_SUITABLE_FOR_CHAR_P
    when C is not a single byte character..  */
 
diff --git a/src/fontset.h b/src/fontset.h
index 5b5c5cbcfaa..c8bd1e36eab 100644
--- a/src/fontset.h
+++ b/src/fontset.h
@@ -66,7 +66,7 @@ struct font_info
   /* Average width of glyphs in the font.  */
   int average_width;
 
-  /* 1 iff `vertical-centering-font-regexp' matches this font name.
+  /* 1 if `vertical-centering-font-regexp' matches this font name.
      In this case, we render characters at vartical center positions
      of lines.  */
   int vertical_centering;
diff --git a/src/getloadavg.c b/src/getloadavg.c
index f40149a8c47..6d66cbfd8a1 100644
--- a/src/getloadavg.c
+++ b/src/getloadavg.c
@@ -484,7 +484,7 @@ static struct dg_sys_info_load_info load_info;	/* what-a-mouthful! */
 #if !defined(HAVE_LIBKSTAT) && defined(LOAD_AVE_TYPE)
 /* File descriptor open to /dev/kmem or VMS load ave driver.  */
 static int channel;
-/* Nonzero iff channel is valid.  */
+/* Nonzero if channel is valid.  */
 static int getloadavg_initialized;
 /* Offset in kmem to seek to read load average, or 0 means invalid.  */
 static long offset;
diff --git a/src/indent.c b/src/indent.c
index 905cf7559a7..b3c1d0cf81a 100644
--- a/src/indent.c
+++ b/src/indent.c
@@ -116,7 +116,7 @@ character_width (c, dp)
     return 0;
 }
 
-/* Return true iff the display table DISPTAB specifies the same widths
+/* Return true if the display table DISPTAB specifies the same widths
    for characters as WIDTHTAB.  We use this to decide when to
    invalidate the buffer's width_run_cache.  */
 
diff --git a/src/indent.h b/src/indent.h
index 2d3c158b069..2e873769603 100644
--- a/src/indent.h
+++ b/src/indent.h
@@ -61,7 +61,7 @@ extern int last_known_column_point;
 
 /* Functions for dealing with the column cache.  */
 
-/* Return true iff the display table DISPTAB specifies the same widths
+/* Return true if the display table DISPTAB specifies the same widths
    for characters as WIDTHTAB.  We use this to decide when to
    invalidate the buffer's column_cache.  */
 int disptab_matches_widthtab P_ ((struct Lisp_Char_Table *disptab,
diff --git a/src/intervals.c b/src/intervals.c
index 89f99a052b9..a695976b8b7 100644
--- a/src/intervals.c
+++ b/src/intervals.c
@@ -2200,7 +2200,7 @@ set_point_both (buffer, charpos, bytepos)
 
   temp_set_point_both (buffer, charpos, bytepos);
 
-  /* We run point-left and point-entered hooks here, iff the
+  /* We run point-left and point-entered hooks here, if the
      two intervals are not equivalent.  These hooks take
      (old_point, new_point) as arguments.  */
   if (NILP (Vinhibit_point_motion_hooks)
diff --git a/src/keyboard.c b/src/keyboard.c
index 5cedd0572b2..171f2da7217 100644
--- a/src/keyboard.c
+++ b/src/keyboard.c
@@ -500,7 +500,7 @@ static struct input_event * volatile kbd_store_ptr;
 /* The above pair of variables forms a "queue empty" flag.  When we
    enqueue a non-hook event, we increment kbd_store_ptr.  When we
    dequeue a non-hook event, we increment kbd_fetch_ptr.  We say that
-   there is input available iff the two pointers are not equal.
+   there is input available if the two pointers are not equal.
 
    Why not just have a flag set and cleared by the enqueuing and
    dequeuing functions?  Such a flag could be screwed up by interrupts
@@ -3590,7 +3590,7 @@ restore_getcjmp (temp)
    kbd_buffer_store_event places events in kbd_buffer, and
    kbd_buffer_get_event retrieves them.  */
 
-/* Return true iff there are any events in the queue that read-char
+/* Return true if there are any events in the queue that read-char
    would return.  If this returns false, a read-char would block.  */
 static int
 readable_events (flags)
diff --git a/src/keyboard.h b/src/keyboard.h
index e24f9a133ae..15e55ad4e67 100644
--- a/src/keyboard.h
+++ b/src/keyboard.h
@@ -240,7 +240,7 @@ extern Lisp_Object item_properties;
 
 /* Macros for dealing with lispy events.  */
 
-/* True iff EVENT has data fields describing it (i.e. a mouse click).  */
+/* True if EVENT has data fields describing it (i.e. a mouse click).  */
 #define EVENT_HAS_PARAMETERS(event) (CONSP (event))
 
 /* Extract the head from an event.
diff --git a/src/keymap.c b/src/keymap.c
index a39c0d43984..e1e45b18d4e 100644
--- a/src/keymap.c
+++ b/src/keymap.c
@@ -4093,7 +4093,7 @@ don't alter it yourself.  */);
   DEFVAR_LISP ("minor-mode-map-alist", &Vminor_mode_map_alist,
 	       doc: /* Alist of keymaps to use for minor modes.
 Each element looks like (VARIABLE . KEYMAP); KEYMAP is used to read
-key sequences and look up bindings iff VARIABLE's value is non-nil.
+key sequences and look up bindings if VARIABLE's value is non-nil.
 If two active keymaps bind the same key, the keymap appearing earlier
 in the list takes precedence.  */);
   Vminor_mode_map_alist = Qnil;
diff --git a/src/lisp.h b/src/lisp.h
index 9a13a95b3b0..7499349a193 100644
--- a/src/lisp.h
+++ b/src/lisp.h
@@ -1441,7 +1441,7 @@ typedef unsigned char UCHAR;
 #define GLYPH_CHAR(f, g) (FAST_GLYPH_CHAR (g))
 #define GLYPH_FACE(f, g) (FAST_GLYPH_FACE (g))
 
-/* Return 1 iff GLYPH contains valid character code.  */
+/* Return 1 if GLYPH contains valid character code.  */
 #define GLYPH_CHAR_VALID_P(glyph) CHAR_VALID_P (FAST_GLYPH_CHAR (glyph), 1)
 
 /* The ID of the mode line highlighting face.  */
@@ -1588,7 +1588,7 @@ typedef unsigned char UCHAR;
    "dead", which is what we want; this is an argument-checking macro, and
    the user should never get access to interior windows.
 
-   A window of any sort, leaf or interior, is dead iff the buffer,
+   A window of any sort, leaf or interior, is dead if the buffer,
    vchild, and hchild members are all nil.  */
 
 #define CHECK_LIVE_WINDOW(x) \
diff --git a/src/lread.c b/src/lread.c
index 5ecb521ff8a..5037937e08b 100644
--- a/src/lread.c
+++ b/src/lread.c
@@ -93,7 +93,7 @@ Lisp_Object Qfile_truename, Qdo_after_load_evaluation; /* ACM 2006/5/16 */
 extern Lisp_Object Qevent_symbol_element_mask;
 extern Lisp_Object Qfile_exists_p;
 
-/* non-zero iff inside `load' */
+/* non-zero if inside `load' */
 int load_in_progress;
 
 /* Directory in which the sources were found.  */
@@ -1126,7 +1126,7 @@ in which case file-name-handlers are ignored.  */)
    On success, returns a file descriptor.  On failure, returns -1.
 
    SUFFIXES is a list of strings containing possible suffixes.
-   The empty suffix is automatically added iff the list is empty.
+   The empty suffix is automatically added if the list is empty.
 
    PREDICATE non-nil means don't open the files,
    just look for one that satisfies the predicate.  In this case,
@@ -4074,7 +4074,7 @@ customize `jka-compr-load-suffixes' rather than the present variable.  */);
   Vload_file_rep_suffixes = Fcons (build_string (""), Qnil);
 
   DEFVAR_BOOL ("load-in-progress", &load_in_progress,
-	       doc: /* Non-nil iff inside of `load'.  */);
+	       doc: /* Non-nil if inside of `load'.  */);
 
   DEFVAR_LISP ("after-load-alist", &Vafter_load_alist,
 	       doc: /* An alist of expressions to be evalled when particular files are loaded.
diff --git a/src/macterm.c b/src/macterm.c
index 87a9861934c..b282bac3aa6 100644
--- a/src/macterm.c
+++ b/src/macterm.c
@@ -11109,7 +11109,7 @@ XTread_socket (sd, expected, hold_quit)
 			  /* Window will be selected only when it is
 			     not selected now and last mouse movement
 			     event was not in it.  Minibuffer window
-			     will be selected iff it is active.  */
+			     will be selected only when it is active.  */
 			  if (WINDOWP (window)
 			      && !EQ (window, last_window)
 			      && !EQ (window, selected_window))
diff --git a/src/macterm.h b/src/macterm.h
index f9ce0ef051d..6a68f39762d 100644
--- a/src/macterm.h
+++ b/src/macterm.h
@@ -150,7 +150,7 @@ struct mac_display_info
   char *mac_id_name;
 
   /* The number of fonts actually stored in the font table.
-     font_table[n] is used and valid iff 0 <= n < n_fonts.  0 <=
+     font_table[n] is used and valid if 0 <= n < n_fonts.  0 <=
      n_fonts <= font_table_size and font_table[i].name != 0.  */
   int n_fonts;
 
diff --git a/src/msdos.c b/src/msdos.c
index 59854268e14..ef65597f7e7 100644
--- a/src/msdos.c
+++ b/src/msdos.c
@@ -3231,7 +3231,7 @@ dos_rawgetc ()
            `dos_get_modifiers', they might have already released the
            Alt key, and Emacs gets just `x', which is BAD.
            However, for keys with the `Map' property set, the ASCII
-           code returns zero iff Alt is pressed.  So, when we DON'T
+           code returns zero only if Alt is pressed.  So, when we DON'T
            have to support international_keyboard, we don't have to
            distinguish between the left and  right Alt keys, and we
            can set the META modifier for any keys with the `Map'
diff --git a/src/process.c b/src/process.c
index 99c5e07f0d4..97bcba3b392 100644
--- a/src/process.c
+++ b/src/process.c
@@ -2781,7 +2781,7 @@ The stopped state is cleared by `continue-process' and set by
 
 :filter-multibyte BOOL -- If BOOL is non-nil, strings given to the
 process filter are multibyte, otherwise they are unibyte.
-If this keyword is not specified, the strings are multibyte iff
+If this keyword is not specified, the strings are multibyte if
 `default-enable-multibyte-characters' is non-nil.
 
 :sentinel SENTINEL -- Install SENTINEL as the process sentinel.
@@ -3920,7 +3920,7 @@ it specifies a fractional number of seconds to wait.
 If optional fourth arg JUST-THIS-ONE is non-nil, only accept output
 from PROCESS, suspending reading output from other processes.
 If JUST-THIS-ONE is an integer, don't run any timers either.
-Return non-nil iff we received any output before the timeout expired.  */)
+Return non-nil if we received any output before the timeout expired.  */)
      (process, seconds, millisec, just_this_one)
      register Lisp_Object process, seconds, millisec, just_this_one;
 {
@@ -4253,16 +4253,16 @@ select_wrapper (n, rfd, wfd, xfd, tmo)
      (and gobble terminal input into the buffer if any arrives).
 
    If WAIT_PROC is specified, wait until something arrives from that
-     process.  The return value is true iff we read some input from
+     process.  The return value is true if we read some input from
      that process.
 
    If JUST_WAIT_PROC is non-nil, handle only output from WAIT_PROC
      (suspending output from other processes).  A negative value
      means don't run any timers either.
 
-   If WAIT_PROC is specified, then the function returns true iff we
+   If WAIT_PROC is specified, then the function returns true if we
      received input from that process before the timeout elapsed.
-   Otherwise, return true iff we received input from any process.  */
+   Otherwise, return true if we received input from any process.  */
 
 int
 wait_reading_process_output (time_limit, microsecs, read_kbd, do_display,
@@ -7324,7 +7324,7 @@ Lisp_Object QCtype;
    do_display != 0 means redisplay should be done to show subprocess
    output that arrives.
 
-   Return true iff we received input from any process.  */
+   Return true if we received input from any process.  */
 
 int
 wait_reading_process_output (time_limit, microsecs, read_kbd, do_display,
diff --git a/src/process.h b/src/process.h
index 6fb783e72b0..2502e61a31d 100644
--- a/src/process.h
+++ b/src/process.h
@@ -138,7 +138,7 @@ extern Lisp_Object chan_process[];
 /* Alist of elements (NAME . PROCESS).  */
 extern Lisp_Object Vprocess_alist;
 
-/* True iff we are about to fork off a synchronous process or if we
+/* True if we are about to fork off a synchronous process or if we
    are waiting for it.  */
 extern int synch_process_alive;
 
diff --git a/src/regex.c b/src/regex.c
index 095afa1c465..6435133c96f 100644
--- a/src/regex.c
+++ b/src/regex.c
@@ -2048,7 +2048,7 @@ re_wctype (str)
   else return 0;
 }
 
-/* True iff CH is in the char class CC.  */
+/* True if CH is in the char class CC.  */
 boolean
 re_iswctype (ch, cc)
      int ch;
diff --git a/src/search.c b/src/search.c
index c74b1071237..3a9fabeb3ce 100644
--- a/src/search.c
+++ b/src/search.c
@@ -1614,7 +1614,7 @@ simple_search (n, pat, len, len_byte, trt, pos, pos_byte, lim, lim_byte)
    have nontrivial translation are the same aside from the last byte.
    This makes it possible to translate just the last byte of a
    character, and do so after just a simple test of the context.
-   CHARSET_BASE is nonzero iff there is such a non-ASCII character.
+   CHARSET_BASE is nonzero if there is such a non-ASCII character.
 
    If that criterion is not satisfied, do not call this function.  */
 
diff --git a/src/systime.h b/src/systime.h
index 85c2799f083..8b1b7f56ad6 100644
--- a/src/systime.h
+++ b/src/systime.h
@@ -67,7 +67,7 @@ extern time_t timezone;
    EMACS_SECS (TIME) is an rvalue for the seconds component of TIME.
    EMACS_SET_SECS (TIME, SECONDS) sets that to SECONDS.
 
-   EMACS_HAS_USECS is defined iff EMACS_TIME has a usecs component.
+   EMACS_HAS_USECS is defined if EMACS_TIME has a usecs component.
    EMACS_USECS (TIME) is an rvalue for the microseconds component of TIME.
    	This returns zero if EMACS_TIME doesn't have a microseconds component.
    EMACS_SET_USECS (TIME, MICROSECONDS) sets that to MICROSECONDS.
@@ -83,7 +83,7 @@ extern time_t timezone;
 
    EMACS_SUB_TIME (DEST, SRC1, SRC2) subtracts SRC2 from SRC1 and
 	stores the result in DEST.  SRC should not be negative.
-   EMACS_TIME_NEG_P (TIME) is true iff TIME is negative.
+   EMACS_TIME_NEG_P (TIME) is true if TIME is negative.
 
 */
 
diff --git a/src/systty.h b/src/systty.h
index 15dd7a4e26c..c89edfc8d93 100644
--- a/src/systty.h
+++ b/src/systty.h
@@ -297,7 +297,7 @@ static struct sensemode {
    written before making the change.
    Return 0 if all went well, and -1 if anything failed.
 
-   EMACS_TTY_TABS_OK (struct emacs_tty *P) is false iff the kernel
+   EMACS_TTY_TABS_OK (struct emacs_tty *P) is false if the kernel
    expands tabs to spaces upon output; in that case, there is no
    advantage to using tabs over spaces.  */
 
diff --git a/src/termhooks.h b/src/termhooks.h
index 5d317f2da3d..32078254593 100644
--- a/src/termhooks.h
+++ b/src/termhooks.h
@@ -201,7 +201,7 @@ extern void (*judge_scroll_bars_hook) P_ ((struct frame *FRAME));
 /* Input queue declarations and hooks.  */
 
 /* Expedient hack: only provide the below definitions to files that
-   are prepared to handle lispy things.  CONSP is defined iff lisp.h
+   are prepared to handle lispy things.  CONSP is defined if lisp.h
    has been included before this file.  */
 #ifdef CONSP
 
diff --git a/src/textprop.c b/src/textprop.c
index 711ee571af6..8ce5656e5a2 100644
--- a/src/textprop.c
+++ b/src/textprop.c
@@ -1633,8 +1633,8 @@ Return t if any property was actually removed, nil otherwise.  */)
      The flag `modified' records if changes have been made.
      When object is a buffer, we must call modify_region before changes are
      made and signal_after_change when we are done.
-     We call modify_region before calling remove_properties iff modified == 0,
-     and we call signal_after_change before returning iff modified != 0. */
+     We call modify_region before calling remove_properties if modified == 0,
+     and we call signal_after_change before returning if modified != 0. */
   for (;;)
     {
       if (i == 0)
diff --git a/src/w32term.c b/src/w32term.c
index b3bf9a0f704..0422257f2d6 100644
--- a/src/w32term.c
+++ b/src/w32term.c
@@ -4336,7 +4336,7 @@ w32_read_socket (sd, expected, hold_quit)
 		  /* Window will be selected only when it is not
 		     selected now and last mouse movement event was
 		     not in it.  Minibuffer window will be selected
-		     iff it is active.  */
+		     only when it is active.  */
 		  if (WINDOWP(window)
 		      && !EQ (window, last_window)
 		      && !EQ (window, selected_window))
diff --git a/src/w32term.h b/src/w32term.h
index 3bf7d588501..acf864d5f38 100644
--- a/src/w32term.h
+++ b/src/w32term.h
@@ -198,7 +198,7 @@ struct w32_display_info
   char *w32_id_name;
 
   /* The number of fonts actually stored in w32_font_table.
-     font_table[n] is used and valid iff 0 <= n < n_fonts. 0 <=
+     font_table[n] is used and valid if 0 <= n < n_fonts. 0 <=
      n_fonts <= font_table_size. and font_table[i].name != 0. */
   int n_fonts;
 
diff --git a/src/window.h b/src/window.h
index a5c1f34a0ce..ea8965392c4 100644
--- a/src/window.h
+++ b/src/window.h
@@ -819,7 +819,7 @@ extern int command_loop_level;
 
 extern int minibuf_level;
 
-/* true iff we should redraw the mode lines on the next redisplay.  */
+/* true if we should redraw the mode lines on the next redisplay.  */
 
 extern int update_mode_lines;
 
diff --git a/src/xterm.c b/src/xterm.c
index 3deb518bad5..00d653fc19f 100644
--- a/src/xterm.c
+++ b/src/xterm.c
@@ -6622,7 +6622,7 @@ handle_one_xevent (dpyinfo, eventp, finish, hold_quit)
 
                 /* Window will be selected only when it is not selected now and
                    last mouse movement event was not in it.  Minibuffer window
-                   will be selected iff it is active.  */
+                   will be selected only when it is active.  */
                 if (WINDOWP (window)
                     && !EQ (window, last_window)
                     && !EQ (window, selected_window))
diff --git a/src/xterm.h b/src/xterm.h
index 84f12d94abd..ad768e36779 100644
--- a/src/xterm.h
+++ b/src/xterm.h
@@ -253,7 +253,7 @@ struct x_display_info
   char *x_id_name;
 
   /* The number of fonts actually stored in x_font_table.
-     font_table[n] is used and valid iff 0 <= n < n_fonts.  0 <=
+     font_table[n] is used and valid if 0 <= n < n_fonts.  0 <=
      n_fonts <= font_table_size and font_table[i].name != 0.  */
   int n_fonts;