diff -u b/core/modules/system/system.api.php b/core/modules/system/system.api.php
--- b/core/modules/system/system.api.php
+++ b/core/modules/system/system.api.php
@@ -1925,23 +1925,21 @@
 /**
  * Logs an event message.
  *
- * This hook allows modules to route log events to custom destinations, such
- * as SMS, Email, pager, syslog, ...etc.
+ * This hook allows modules to route log events to custom destinations, such as
+ * SMS, Email, pager, syslog, ...etc.
  *
  * @param array $log_entry
  *   An associative array containing the following keys:
  *   - type: The type of message for this entry. For contributed modules, this
- *     is normally the module name. Do not use 'debug'; use severity
- *     WATCHDOG_DEBUG instead.
+ *     is normally the module name.
  *   - user: The user object for the user who was logged in when the event
  *     happened.
- *   - request_uri: The Request URI for the page the event happened in.
- *   - referer: The page that referred the use to the page where the event
+ *   - request_uri: The request URI for the page the event happened in.
+ *   - referer: The page that referred the user to the page where the event
  *     occurred.
  *   - ip: The IP address where the request for the page came from.
  *   - timestamp: The UNIX timestamp of the date/time the event occurred.
- *   - severity: One of the following values as defined in @link
- *     http://www.faqs.org/rfcs/rfc3164.html RFC 3164 @endlink
+ *   - severity: One of the following values as defined in @link http://www.faqs.org/rfcs/rfc3164.html RFC 3164 @endlink
  *     - WATCHDOG_EMERGENCY: Emergency, system is unusable.
  *     - WATCHDOG_ALERT: Alert, action must be taken immediately.
  *     - WATCHDOG_CRITICAL: Critical conditions.
@@ -1953,12 +1951,12 @@
  *   - link: An optional link provided by the module that called the watchdog()
  *     function.
  *   - message: The text of the message to be logged. Variables in the message
- *     should be added by using placeholder strings alongside the variables
+ *     are indicated by using placeholder strings alongside the variables
  *     argument to declare the value of the placeholders. See t() for
  *     documentation on how the message and variable parameters interact.
  *   - variables: An array of variables to be inserted into the message on
- *     display. Set this to NULL if a message is already translated or if the
- *     message is not possible to translate. Defaults to NULL.
+ *     display. Will be NULL or missing if a message is already translated or if
+ *     the message is not possible to translate. Defaults to NULL.
  */
 function hook_watchdog(array $log_entry) {
   global $base_url, $language_interface;
only in patch2:
unchanged:
--- a/core/includes/bootstrap.inc
+++ b/core/includes/bootstrap.inc
@@ -72,32 +72,32 @@ const WATCHDOG_EMERGENCY = 0;
 const WATCHDOG_ALERT = 1;
 
 /**
- * Log message severity -- Critical: critical conditions.
+ * Log message severity -- Critical conditions.
  */
 const WATCHDOG_CRITICAL = 2;
 
 /**
- * Log message severity -- Error: error conditions.
+ * Log message severity -- Error conditions.
  */
 const WATCHDOG_ERROR = 3;
 
 /**
- * Log message severity -- Warning: warning conditions.
+ * Log message severity -- Warning conditions.
  */
 const WATCHDOG_WARNING = 4;
 
 /**
- * Log message severity -- Notice: normal but significant condition.
+ * Log message severity -- Normal but significant conditions.
  */
 const WATCHDOG_NOTICE = 5;
 
 /**
- * Log message severity -- Informational: informational messages.
+ * Log message severity -- Informational messages.
  */
 const WATCHDOG_INFO = 6;
 
 /**
- * Log message severity -- Debug: debug-level messages.
+ * Log message severity -- Debug-level messages.
  */
 const WATCHDOG_DEBUG = 7;