Fix typo.

lisp/calc/calc-alg.el

@@ -1294,7 +1294,7 @@
 
 ;;; Simple operations on expressions.
 
-;;; Return number of ocurrences of thing in expr, or nil if none.
+;;; Return number of occurrences of thing in expr, or nil if none.
 (defun math-expr-contains-count (expr thing)
   (cond ((equal expr thing) 1)
 	((Math-primp expr) nil)

man/reftex.texi

@@ -1399,7 +1399,7 @@ to search backward for these macros.  When the first match is
 @code{\ee}, point is not in this environment.  When the first match is
 @code{\be}, point is in this environment and the function must return
 the beginning of the match.  To avoid scanning too far, we can also look
-for empty lines which cannot occure inside an equation environment.
+for empty lines which cannot occur inside an equation environment.
 Here is the setup:@refill
 
 @lisp

src/macfns.c

@@ -6987,7 +6987,7 @@ pbm_scan_number (s, end)
 
 /* Read FILE into memory.  Value is a pointer to a buffer allocated
    with xmalloc holding FILE's contents.  Value is null if an error
-   occured.  *SIZE is set to the size of the file.  */
+   occurred.  *SIZE is set to the size of the file.  */
 
 static char *
 pbm_read_file (file, size)

src/msdos.c

@@ -5007,7 +5007,7 @@ static sigset_t pending_signals;
 typedef void (*sighandler_t)(int);
 static sighandler_t prev_handlers[320];
 
-/* A signal handler which just records that a signal occured
+/* A signal handler which just records that a signal occurred
    (it will be raised later, if and when the signal is unblocked).  */
 static void
 sig_suspender (signo)

src/w32fns.c

@@ -11207,7 +11207,7 @@ pbm_scan_number (s, end)
 
 /* Read FILE into memory.  Value is a pointer to a buffer allocated
    with xmalloc holding FILE's contents.  Value is null if an error
-   occured.  *SIZE is set to the size of the file.  */
+   occurred.  *SIZE is set to the size of the file.  */
 
 static char *
 pbm_read_file (file, size)