diff --git a/framework/yii/base/Event.php b/framework/yii/base/Event.php
index 99f8492..4ba8c7d 100644
--- a/framework/yii/base/Event.php
+++ b/framework/yii/base/Event.php
@@ -25,13 +25,15 @@ namespace yii\base;
 class Event extends Object
 {
 	/**
-	 * @var string the event name. This property is set by [[Component::trigger()]].
+	 * @var string the event name. This property is set by [[Component::trigger()]] and [[trigger()]].
 	 * Event handlers may use this property to check what event it is handling.
 	 */
 	public $name;
 	/**
 	 * @var object the sender of this event. If not set, this property will be
 	 * set as the object whose "trigger()" method is called.
+	 * This property may also be a `null` when this event is a
+	 * class-level event which is triggered in a static context.
 	 */
 	public $sender;
 	/**
@@ -88,7 +90,7 @@ class Event extends Object
 	 * @param string $name the event name.
 	 * @param callback $handler the event handler to be removed.
 	 * If it is null, all handlers attached to the named event will be removed.
-	 * @return boolean if a handler is found and detached.
+	 * @return boolean whether a handler is found and detached.
 	 * @see on()
 	 */
 	public static function off($class, $name, $handler = null)