diff -u b/core/includes/bootstrap.inc b/core/includes/bootstrap.inc
--- b/core/includes/bootstrap.inc
+++ b/core/includes/bootstrap.inc
@@ -1568,8 +1568,16 @@
  *   NULL if message is already translated or not possible to
  *   translate.
  * @param $severity
- *   The severity of the message, as per RFC 3164. Possible values are
- *   WATCHDOG_ERROR, WATCHDOG_WARNING, etc.
+ *   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.
+ *     - WATCHDOG_ERROR: Error conditions.
+ *     - WATCHDOG_WARNING: Warning conditions.
+ *     - WATCHDOG_NOTICE: Normal but significant conditions.
+ *     - WATCHDOG_INFO: Informational messages.
+ *     - WATCHDOG_DEBUG: Debug-level messages.
  * @param $link
  *   A link to associate with the message.
  *
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
@@ -1923,15 +1923,14 @@
 }
 
 /**
- * Logs an event message.
+ * Log an event message.
  *
  * 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.
+ *   - type: The type of message for this entry.
  *   - 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.
@@ -1939,7 +1938,8 @@
  *     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.
@@ -1956,7 +1956,7 @@
  *     documentation on how the message and variable parameters interact.
  *   - variables: An array of variables to be inserted into the message on
  *     display. Will be NULL or missing if a message is already translated or if
- *     the message is not possible to translate. Defaults to NULL.
+ *     the message is not possible to translate.
  */
 function hook_watchdog(array $log_entry) {
   global $base_url, $language_interface;