diff --git a/core/lib/Drupal/Core/Queue/Memory.php b/core/lib/Drupal/Core/Queue/Memory.php
index 125d146..54a4f65 100644
--- a/core/lib/Drupal/Core/Queue/Memory.php
+++ b/core/lib/Drupal/Core/Queue/Memory.php
@@ -31,6 +31,8 @@ class Memory implements QueueInterface {
    */
   protected $id_sequence;
 
+  /* Implementations of Drupal\Core\Queue\QueueInterface. */
+
   public function __construct($name) {
     $this->queue = array();
     $this->id_sequence = 0;
diff --git a/core/lib/Drupal/Core/Queue/QueueInterface.php b/core/lib/Drupal/Core/Queue/QueueInterface.php
index 3b0b35f..90d4b00 100644
--- a/core/lib/Drupal/Core/Queue/QueueInterface.php
+++ b/core/lib/Drupal/Core/Queue/QueueInterface.php
@@ -23,10 +23,11 @@ interface QueueInterface {
   public function __construct($name);
 
   /**
-   * Add a queue item and store it directly to the queue.
+   * Adds a queue item and store it directly to the queue.
    *
    * @param $data
    *   Arbitrary data to be associated with the new task in the queue.
+   *
    * @return
    *   TRUE if the item was successfully created and was (best effort) added
    *   to the queue, otherwise FALSE. We don't guarantee the item was
@@ -36,7 +37,7 @@ interface QueueInterface {
   public function createItem($data);
 
   /**
-   * Retrieve the number of items in the queue.
+   * Retrieves the number of items in the queue.
    *
    * This is intended to provide a "best guess" count of the number of items in
    * the queue. Depending on the implementation and the setup, the accuracy of
@@ -52,7 +53,7 @@ interface QueueInterface {
   public function numberOfItems();
 
   /**
-   * Claim an item in the queue for processing.
+   * Claims an item in the queue for processing.
    *
    * @param $lease_time
    *   How long the processing is expected to take in seconds, defaults to an
@@ -63,6 +64,7 @@ interface QueueInterface {
    *   run more than once (non-idempotent), a larger lease time will make it
    *   more rare for a given task to run multiple times in cases of failure,
    *   at the cost of higher latency.
+   *
    * @return
    *   On success we return an item object. If the queue is unable to claim an
    *   item it returns false. This implies a best effort to retrieve an item
@@ -72,7 +74,7 @@ interface QueueInterface {
   public function claimItem($lease_time = 3600);
 
   /**
-   * Delete a finished item from the queue.
+   * Deletes a finished item from the queue.
    *
    * @param $item
    *   The item returned by Drupal\Core\Queue\QueueInterface::claimItem().
@@ -80,16 +82,20 @@ interface QueueInterface {
   public function deleteItem($item);
 
   /**
-   * Release an item that the worker could not process, so another
-   * worker can come in and process it before the timeout expires.
+   * Releases an item that the worker could not process.
+   *
+   * Another worker can come in and process it before the timeout expires.
    *
    * @param $item
+   *   The item returned by Drupal\Core\Queue\QueueInterface::claimItem().
+   *
    * @return boolean
+   *   TRUE if the item has been released, FALSE otherwise.
    */
   public function releaseItem($item);
 
   /**
-   * Create a queue.
+   * Creates a queue.
    *
    * Called during installation and should be used to perform any necessary
    * initialization operations. This should not be confused with the
@@ -102,7 +108,7 @@ interface QueueInterface {
   public function createQueue();
 
   /**
-   * Delete a queue and every item in the queue.
+   * Deletes a queue and every item in the queue.
    */
   public function deleteQueue();
 }
diff --git a/core/lib/Drupal/Core/Queue/System.php b/core/lib/Drupal/Core/Queue/System.php
index bc4d68e..f89f98b 100644
--- a/core/lib/Drupal/Core/Queue/System.php
+++ b/core/lib/Drupal/Core/Queue/System.php
@@ -18,6 +18,8 @@ class System implements ReliableQueueInterface {
    */
   protected $name;
 
+  /* Implementations of Drupal\Core\Queue\ReliableQueueInterface. */
+
   public function __construct($name) {
     $this->name = $name;
   }