diff --git a/core/lib/Drupal/Core/Cache/DatabaseBackend.php b/core/lib/Drupal/Core/Cache/DatabaseBackend.php
index 8a2d414..774ea05 100644
--- a/core/lib/Drupal/Core/Cache/DatabaseBackend.php
+++ b/core/lib/Drupal/Core/Cache/DatabaseBackend.php
@@ -175,6 +175,12 @@ public function set($cid, $data, $expire = Cache::PERMANENT, array $tags = array
 
   /**
    * Calculate a consistent-length cache ID.
+   *
+   * @param string $cid
+   *   A cache ID of any length.
+   *
+   * @return string
+   *   A base64 encoded hash of the cache ID.
    */
   protected static function cidhash($cid) {
     return rtrim(base64_encode(hash('sha256', $cid, TRUE)), '=');
@@ -580,14 +586,14 @@ public function schemaDefinition() {
       'description' => 'Storage for the cache API.',
       'fields' => array(
         'cidhash' => array(
-          'description' => 'Hash of the human-readable cid.',
+          'description' => 'Hash of the human-readable cache ID.',
           'type' => 'varchar',
           'length' => $hash_length,
           // Use a more optimal data type for MySQL.
           'mysql_type' => "BINARY($hash_length)",
         ),
         'cid' => array(
-          'description' => 'Original (human-readable) Cache ID.',
+          'description' => 'Original (human-readable) cache ID.',
           'type' => 'varchar',
           'length' => 1000,
           'not null' => TRUE,
diff --git a/core/lib/Drupal/Core/Cache/PhpBackend.php b/core/lib/Drupal/Core/Cache/PhpBackend.php
index dfc1560..73153c9 100644
--- a/core/lib/Drupal/Core/Cache/PhpBackend.php
+++ b/core/lib/Drupal/Core/Cache/PhpBackend.php
@@ -53,10 +53,11 @@ public function get($cid, $allow_invalid = FALSE) {
   }
 
   /**
-   * Fetch a cache entry using a hashed cache ID.
+   * Fetch a cache item using a hashed cache ID.
    *
    * @param string $cidhash
-   *   The value after applying Crypt::hashBase64() to the original cache ID.
+   *   The hashed version of the original cache ID after applying
+   *   Crypt::hashBase64().
    * @param bool $allow_invalid
    *   (optional) If TRUE, a cache item may be returned even if it is expired or
    *   has been invalidated.
@@ -187,10 +188,11 @@ public function invalidate($cid) {
   }
 
   /**
-   * Invalidate one cache entry.
+   * Invalidate one cache item.
    *
    * @param string $cidhash
-   *   The value after applying Crypt::hashBase64() to the original cache ID.
+   *   The hashed version of the original cache ID after applying
+   *   Crypt::hashBase64().
    */
   protected function invalidatebyHash($cidhash) {
     if ($item = $this->getByHash($cidhash)) {
@@ -276,7 +278,8 @@ public function removeBin() {
    * Writes a cache item to PhpStorage.
    *
    * @param string $cidhash
-   *   The hashed cache ID of the data to store.
+   *   The hashed version of the original cache ID after applying
+   *   Crypt::hashBase64().
    * @param \stdClass $item
    *   The cache item to store.
    */
diff --git a/core/modules/system/lib/Drupal/system/Tests/Cache/GenericCacheBackendUnitTestBase.php b/core/modules/system/lib/Drupal/system/Tests/Cache/GenericCacheBackendUnitTestBase.php
index 07b1dac..35635e8 100644
--- a/core/modules/system/lib/Drupal/system/Tests/Cache/GenericCacheBackendUnitTestBase.php
+++ b/core/modules/system/lib/Drupal/system/Tests/Cache/GenericCacheBackendUnitTestBase.php
@@ -384,7 +384,7 @@ public function testSetMultiple() {
   public function testDeleteMultiple() {
     $backend = $this->getCacheBackend();
 
-    // Calling delete with an empty list should not cause an error.
+    // Calling deleteMultiple() with an empty array should not cause an error.
     $backend->deleteMultiple(array());
 
     // Set numerous testing keys.
@@ -518,7 +518,8 @@ function testInvalidate() {
     $ret = $backend->getMultiple($cids);
     $this->assertEqual(count($ret), 4, 'Four items returned.');
 
-    // Calling invalidate with an empty list should not cause an error.
+    // Calling invalidateMultiple() with an empty array should not cause an
+    // error.
     $backend->invalidateMultiple(array());
 
     $backend->invalidate('test1');