diff --git a/src/core/ngx_cycle.c b/src/core/ngx_cycle.c
index 968056c..db47357 100644
--- a/src/core/ngx_cycle.c
+++ b/src/core/ngx_cycle.c
@@ -739,7 +739,7 @@
         ngx_temp_pool = ngx_create_pool(128, cycle->log);
         if (ngx_temp_pool == NULL) {
             ngx_log_error(NGX_LOG_EMERG, cycle->log, 0,
-                          "can not create ngx_temp_pool");
+                          "could not create ngx_temp_pool");
             exit(1);
         }
 
diff --git a/src/core/ngx_palloc.c b/src/core/ngx_palloc.c
index 35f1311..9eac114 100644
--- a/src/core/ngx_palloc.c
+++ b/src/core/ngx_palloc.c
@@ -68,7 +68,7 @@
 
     /*
      * we could allocate the pool->log from this pool
-     * so we can not use this log while the free()ing the pool
+     * so we cannot use this log while free()ing the pool
      */
 
     for (p = pool, n = pool->d.next; /* void */; p = n, n = n->d.next) {
diff --git a/src/core/ngx_string.c b/src/core/ngx_string.c
index 4dcfe01..75bc657 100644
--- a/src/core/ngx_string.c
+++ b/src/core/ngx_string.c
@@ -381,7 +381,7 @@
 
                     /*
                      * (int64_t) cast is required for msvc6:
-                     * it can not convert uint64_t to double
+                     * it cannot convert uint64_t to double
                      */
                     ui64 = (uint64_t) ((f - (int64_t) ui64) * scale + 0.5);
 
diff --git a/src/event/ngx_event.c b/src/event/ngx_event.c
index c57d37e..8a472ff 100644
--- a/src/event/ngx_event.c
+++ b/src/event/ngx_event.c
@@ -1027,7 +1027,7 @@
                                "when the server runs without a master process "
                                "the \"%V\" event type must be the same as "
                                "in previous configuration - \"%s\" "
-                               "and it can not be changed on the fly, "
+                               "and it cannot be changed on the fly, "
                                "to change it you need to stop server "
                                "and start it again",
                                &value[1], old_ecf->name);
diff --git a/src/event/ngx_event_timer.c b/src/event/ngx_event_timer.c
index 2931a9f..76a1a1f 100644
--- a/src/event/ngx_event_timer.c
+++ b/src/event/ngx_event_timer.c
@@ -103,11 +103,11 @@
             if (ngx_threaded && ngx_trylock(ev->lock) == 0) {
 
                 /*
-                 * We can not change the timer of the event that is been
-                 * handling by another thread.  And we can not easy walk
-                 * the rbtree to find a next expired timer so we exit the loop.
-                 * However it should be rare case when the event that is
-                 * been handling has expired timer.
+                 * We cannot change the timer of the event that is being
+                 * handled by another thread.  And we cannot easy walk
+                 * the rbtree to find next expired timer so we exit the loop.
+                 * However, it should be a rare case when the event that is
+                 * being handled has an expired timer.
                  */
 
                 ngx_log_debug1(NGX_LOG_DEBUG_EVENT, ev->log, 0,
diff --git a/src/http/modules/ngx_http_dav_module.c b/src/http/modules/ngx_http_dav_module.c
index 0761c16..3bd9d3e 100644
--- a/src/http/modules/ngx_http_dav_module.c
+++ b/src/http/modules/ngx_http_dav_module.c
@@ -158,7 +158,7 @@
 
         if (r->uri.data[r->uri.len - 1] == '/') {
             ngx_log_error(NGX_LOG_ERR, r->connection->log, 0,
-                          "can not PUT to a collection");
+                          "cannot PUT to a collection");
             return NGX_HTTP_CONFLICT;
         }
 
diff --git a/src/http/modules/ngx_http_headers_filter_module.c b/src/http/modules/ngx_http_headers_filter_module.c
index 1d40958..c3f74ae 100644
--- a/src/http/modules/ngx_http_headers_filter_module.c
+++ b/src/http/modules/ngx_http_headers_filter_module.c
@@ -507,7 +507,7 @@
         minus = 0;
 
         if (hcf->expires == NGX_HTTP_EXPIRES_MODIFIED) {
-            return "daily time can not be used with \"modified\" parameter";
+            return "daily time cannot be used with \"modified\" parameter";
         }
 
         hcf->expires = NGX_HTTP_EXPIRES_DAILY;
diff --git a/src/http/modules/ngx_http_log_module.c b/src/http/modules/ngx_http_log_module.c
index b2bfbf4..9728d54 100644
--- a/src/http/modules/ngx_http_log_module.c
+++ b/src/http/modules/ngx_http_log_module.c
@@ -960,7 +960,7 @@
 
         if (log->script) {
             ngx_conf_log_error(NGX_LOG_EMERG, cf, 0,
-                               "buffered logs can not have variables in name");
+                               "buffered logs cannot have variables in name");
             return NGX_CONF_ERROR;
         }
 
diff --git a/src/http/ngx_http.c b/src/http/ngx_http.c
index 5ca9fed..e809045 100644
--- a/src/http/ngx_http.c
+++ b/src/http/ngx_http.c
@@ -1226,7 +1226,7 @@
 #endif
 
     /*
-     * we can not compare whole sockaddr struct's as kernel
+     * we cannot compare whole sockaddr struct's as kernel
      * may fill some fields in inherited sockaddr struct's
      */
 
diff --git a/src/http/ngx_http_core_module.c b/src/http/ngx_http_core_module.c
index 0fb5012..d51dc23 100644
--- a/src/http/ngx_http_core_module.c
+++ b/src/http/ngx_http_core_module.c
@@ -3191,7 +3191,7 @@
                               prev->underscores_in_headers, 0);
 
     if (conf->server_names.nelts == 0) {
-        /* the array has 4 empty preallocated elements, so push can not fail */
+        /* the array has 4 empty preallocated elements, so push cannot fail */
         sn = ngx_array_push(&conf->server_names);
 #if (NGX_PCRE)
         sn->regex = NULL;
diff --git a/src/os/unix/ngx_errno.c b/src/os/unix/ngx_errno.c
index 02994b8..faae478 100644
--- a/src/os/unix/ngx_errno.c
+++ b/src/os/unix/ngx_errno.c
@@ -12,7 +12,7 @@
  * The strerror() messages are copied because:
  *
  * 1) strerror() and strerror_r() functions are not Async-Signal-Safe,
- *    therefore, they can not be used in signal handlers;
+ *    therefore, they cannot be used in signal handlers;
  *
  * 2) a direct sys_errlist[] array may be used instead of these functions,
  *    but Linux linker warns about its usage:
diff --git a/src/os/unix/ngx_file_aio_read.c b/src/os/unix/ngx_file_aio_read.c
index 557f9de..4966236 100644
--- a/src/os/unix/ngx_file_aio_read.c
+++ b/src/os/unix/ngx_file_aio_read.c
@@ -23,7 +23,7 @@
  *    kqueue EVFILT_AIO filter is level triggered only: an event repeats
  *    until aio_return() will be called;
  *
- *    aio_cancel() can not cancel file AIO: it returns AIO_NOTCANCELED always.
+ *    aio_cancel() cannot cancel file AIO: it returns AIO_NOTCANCELED always.
  */
 
 
diff --git a/src/os/unix/ngx_freebsd_sendfile_chain.c b/src/os/unix/ngx_freebsd_sendfile_chain.c
index 70cdb74..039243e 100644
--- a/src/os/unix/ngx_freebsd_sendfile_chain.c
+++ b/src/os/unix/ngx_freebsd_sendfile_chain.c
@@ -11,7 +11,7 @@
 
 /*
  * Although FreeBSD sendfile() allows to pass a header and a trailer,
- * it can not send a header with a part of the file in one packet until
+ * it cannot send a header with a part of the file in one packet until
  * FreeBSD 5.3.  Besides, over the fast ethernet connection sendfile()
  * may send the partially filled packets, i.e. the 8 file pages may be sent
  * as the 11 full 1460-bytes packets, then one incomplete 324-bytes packet,
diff --git a/src/os/unix/ngx_process.c b/src/os/unix/ngx_process.c
index ad2fc19..08069c4 100644
--- a/src/os/unix/ngx_process.c
+++ b/src/os/unix/ngx_process.c
@@ -541,7 +541,7 @@
         if (WEXITSTATUS(status) == 2 && ngx_processes[i].respawn) {
             ngx_log_error(NGX_LOG_ALERT, ngx_cycle->log, 0,
                           "%s %P exited with fatal code %d "
-                          "and can not be respawn",
+                          "and cannot be respawned",
                           process, pid, WEXITSTATUS(status));
             ngx_processes[i].respawn = 0;
         }
diff --git a/src/os/unix/ngx_process_cycle.c b/src/os/unix/ngx_process_cycle.c
index 3ff0f75..863176f 100644
--- a/src/os/unix/ngx_process_cycle.c
+++ b/src/os/unix/ngx_process_cycle.c
@@ -620,7 +620,8 @@
                     == NGX_INVALID_PID)
                 {
                     ngx_log_error(NGX_LOG_ALERT, cycle->log, 0,
-                                  "can not respawn %s", ngx_processes[i].name);
+                                  "could not respawn %s",
+                                  ngx_processes[i].name);
                     continue;
                 }
 
diff --git a/src/os/win32/ngx_process_cycle.c b/src/os/win32/ngx_process_cycle.c
index 1037910..c446572 100644
--- a/src/os/win32/ngx_process_cycle.c
+++ b/src/os/win32/ngx_process_cycle.c
@@ -530,7 +530,7 @@
                 == NGX_INVALID_PID)
             {
                 ngx_log_error(NGX_LOG_ALERT, cycle->log, 0,
-                              "can not respawn %s", ngx_processes[n].name);
+                              "could not respawn %s", ngx_processes[n].name);
 
                 if (n == ngx_last_process - 1) {
                     ngx_last_process--;