diff --git a/core/modules/aggregator/aggregator.module b/core/modules/aggregator/aggregator.module
index 047026a..d13bee8 100644
--- a/core/modules/aggregator/aggregator.module
+++ b/core/modules/aggregator/aggregator.module
@@ -405,7 +405,7 @@ function aggregator_block_view($delta = '') {
     switch ($type) {
       case 'feed':
         if ($feed = db_query('SELECT fid, title, block FROM {aggregator_feed} WHERE block <> 0 AND fid = :fid', array(':fid' => $id))->fetchObject()) {
-          $block['subject'] = check_plain($feed->title);
+          $block['default_title'] = check_plain($feed->title);
           $result = db_query_range("SELECT * FROM {aggregator_item} WHERE fid = :fid ORDER BY timestamp DESC, iid DESC", 0, $feed->block, array(':fid' => $id));
           $read_more = theme('more_link', array('url' => 'aggregator/sources/' . $feed->fid, 'title' => t("View this feed's recent news.")));
         }
@@ -413,7 +413,7 @@ function aggregator_block_view($delta = '') {
 
       case 'category':
         if ($category = db_query('SELECT cid, title, block FROM {aggregator_category} WHERE cid = :cid', array(':cid' => $id))->fetchObject()) {
-          $block['subject'] = check_plain($category->title);
+          $block['default_title'] = check_plain($category->title);
           $result = db_query_range('SELECT i.* FROM {aggregator_category_item} ci LEFT JOIN {aggregator_item} i ON ci.iid = i.iid WHERE ci.cid = :cid ORDER BY i.timestamp DESC, i.iid DESC', 0, $category->block, array(':cid' => $category->cid));
           $read_more = theme('more_link', array('url' => 'aggregator/categories/' . $category->cid, 'title' => t("View this category's recent news.")));
         }
diff --git a/core/modules/block/block.admin.inc b/core/modules/block/block.admin.inc
index cc4bd71..c030d99 100644
--- a/core/modules/block/block.admin.inc
+++ b/core/modules/block/block.admin.inc
@@ -276,7 +276,7 @@ function block_admin_configure($form, &$form_state, $module, $delta) {
     '#value' => $block->delta,
   );
 
-  // Get the block subject for the page title.
+  // Get the block default_title for the page title.
   $info = module_invoke($block->module, 'block_info');
   if (isset($info[$block->delta])) {
     drupal_set_title(t("'%name' block", array('%name' => $info[$block->delta]['info'])), PASS_THROUGH);
diff --git a/core/modules/block/block.api.php b/core/modules/block/block.api.php
index b734685..dee2b15 100644
--- a/core/modules/block/block.api.php
+++ b/core/modules/block/block.api.php
@@ -203,8 +203,8 @@ function hook_block_save($delta = '', $edit = array()) {
  *
  * @return
  *   An array containing the following elements:
- *   - subject: The default localized title of the block. If the block does not
- *     have a default title, this should be set to NULL.
+ *   - default_title: The default localized title of the block. If the block
+ *     does not have a default title, this should be set to NULL.
  *   - content: The content of the block's body. This may be a renderable array
  *     (preferable) or a string containing rendered HTML content.
  *
@@ -220,7 +220,7 @@ function hook_block_view($delta = '') {
 
   switch ($delta) {
     case 'syndicate':
-      $block['subject'] = t('Syndicate');
+      $block['default_title'] = t('Syndicate');
       $block['content'] = array(
         '#theme' => 'feed_icon',
         '#url' => 'rss.xml',
@@ -230,7 +230,7 @@ function hook_block_view($delta = '') {
 
     case 'recent':
       if (user_access('access content')) {
-        $block['subject'] = t('Recent content');
+        $block['default_title'] = t('Recent content');
         if ($nodes = node_get_recent(variable_get('node_recent_block_count', 10))) {
           $block['content'] = array(
             '#theme' => 'node_recent_block',
@@ -291,7 +291,7 @@ function hook_block_view_alter(&$data, $block) {
  * @param $data
  *   An array of data, as returned from the hook_block_view() implementation of
  *   the module that defined the block:
- *   - subject: The localized title of the block.
+ *   - default_title: The localized title of the block.
  *   - content: Either a string or a renderable array representing the content
  *     of the block. You should check that the content is an array before trying
  *     to modify parts of the renderable structure.
@@ -311,7 +311,7 @@ function hook_block_view_MODULE_DELTA_alter(&$data, $block) {
 
   // Change the title of the "somedelta" block provided by the "mymodule"
   // module.
-  $data['subject'] = t('New title of the block');
+  $data['default_title'] = t('New title of the block');
 }
 
 /**
diff --git a/core/modules/block/block.module b/core/modules/block/block.module
index 0626c08..640b614 100644
--- a/core/modules/block/block.module
+++ b/core/modules/block/block.module
@@ -253,7 +253,7 @@ function block_block_save($delta = 0, $edit = array()) {
  */
 function block_block_view($delta = '') {
   $block = db_query('SELECT body, format FROM {block_custom} WHERE bid = :bid', array(':bid' => $delta))->fetchObject();
-  $data['subject'] = NULL;
+  $data['default_title'] = NULL;
   $data['content'] = check_markup($block->body, $block->format, '', TRUE);
   return $data;
 }
@@ -759,7 +759,7 @@ function _block_load_blocks() {
   global $theme_key;
 
   $query = db_select('block', 'b');
-  $query->addField('b', 'title', 'subject');
+  $query->addField('b', 'title', 'default_title');
   $result = $query
     ->fields('b')
     ->condition('b.theme', $theme_key)
@@ -936,7 +936,7 @@ function _block_get_renderable_block($element) {
     if ($block->title) {
       // Check plain here to allow module generated titles to keep any
       // markup.
-      $block->subject = $block->title == '<none>' ? '' : check_plain($block->title);
+      $block->default_title = $block->title == '<none>' ? '' : check_plain($block->title);
     }
 
     // Add the content renderable array to the main element.
diff --git a/core/modules/block/lib/Drupal/block/Tests/BlockTest.php b/core/modules/block/lib/Drupal/block/Tests/BlockTest.php
index 1b598e3..0fee7bd 100644
--- a/core/modules/block/lib/Drupal/block/Tests/BlockTest.php
+++ b/core/modules/block/lib/Drupal/block/Tests/BlockTest.php
@@ -103,7 +103,7 @@ function testCustomBlock() {
     // Check that block_block_view() returns the correct title and content.
     $data = block_block_view($bid);
     $format = db_query("SELECT format FROM {block_custom} WHERE bid = :bid", array(':bid' => $bid))->fetchField();
-    $this->assertTrue(array_key_exists('subject', $data) && empty($data['subject']), 'block_block_view() provides an empty block subject, since custom blocks do not have default titles.');
+    $this->assertTrue(array_key_exists('default_title', $data) && empty($data['default_title']), t('block_block_view() provides an empty block default_title, since custom blocks do not have default titles.'));
     $this->assertEqual(check_markup($custom_block['body[value]'], $format), $data['content'], 'block_block_view() provides correct block content.');
 
     // Check whether the block can be moved to all available regions.
diff --git a/core/modules/block/templates/block.tpl.php b/core/modules/block/templates/block.tpl.php
index 895b49f..e12757a 100644
--- a/core/modules/block/templates/block.tpl.php
+++ b/core/modules/block/templates/block.tpl.php
@@ -5,7 +5,7 @@
  * Default theme implementation to display a block.
  *
  * Available variables:
- * - $block->subject: Block title.
+ * - $block->default_title: Block title.
  * - $content: Block content.
  * - $block->module: Module that generated the block.
  * - $block->delta: An ID for the block, unique within each module.
@@ -44,8 +44,8 @@
 <div id="<?php print $block_html_id; ?>" <?php print $attributes; ?>>
 
   <?php print render($title_prefix); ?>
-<?php if ($block->subject): ?>
-  <h2<?php print $title_attributes; ?>><?php print $block->subject ?></h2>
+<?php if ($block->default_title): ?>
+  <h2<?php print $title_attributes; ?>><?php print $block->default_title ?></h2>
 <?php endif;?>
   <?php print render($title_suffix); ?>
 
diff --git a/core/modules/book/book.module b/core/modules/book/book.module
index fd4fac9..120bfcf 100644
--- a/core/modules/book/book.module
+++ b/core/modules/book/book.module
@@ -286,7 +286,7 @@ function book_block_view($delta = '') {
   }
 
   if (config('book.settings')->get('block.navigation.mode') == 'all pages') {
-    $block['subject'] = t('Book navigation');
+    $block['default_title'] = t('Book navigation');
     $book_menus = array();
     $pseudo_tree = array(0 => array('below' => FALSE));
     foreach (book_get_books() as $book_id => $book) {
@@ -322,7 +322,7 @@ function book_block_view($delta = '') {
       $tree = menu_tree_all_data($node->book['menu_name'], $node->book);
       // There should only be one element at the top level.
       $data = array_shift($tree);
-      $block['subject'] = theme('book_title_link', array('link' => $data['link']));
+      $block['default_title'] = theme('book_title_link', array('link' => $data['link']));
       $block['content'] = ($data['below']) ? menu_tree_output($data['below']) : '';
     }
   }
diff --git a/core/modules/comment/comment.module b/core/modules/comment/comment.module
index 27ff7c3..9101db3 100644
--- a/core/modules/comment/comment.module
+++ b/core/modules/comment/comment.module
@@ -479,7 +479,7 @@ function comment_block_save($delta = '', $edit = array()) {
  */
 function comment_block_view($delta = '') {
   if (user_access('access comments')) {
-    $block['subject'] = t('Recent comments');
+    $block['default_title'] = t('Recent comments');
     $block['content'] = theme('comment_block');
 
     return $block;
diff --git a/core/modules/forum/forum.module b/core/modules/forum/forum.module
index f365491..9b9d146 100644
--- a/core/modules/forum/forum.module
+++ b/core/modules/forum/forum.module
@@ -703,7 +703,7 @@ function forum_block_view($delta = '') {
       break;
   }
 
-  $block['subject'] = $title;
+  $block['default_title'] = $title;
   // Cache based on the altered query. Enables us to cache with node access enabled.
   $block['content'] = drupal_render_cache_by_query($query, 'forum_block_view');
   $block['content']['#access'] = user_access('access content');
diff --git a/core/modules/language/language.module b/core/modules/language/language.module
index 5b62382..8f691df 100644
--- a/core/modules/language/language.module
+++ b/core/modules/language/language.module
@@ -541,7 +541,7 @@ function language_block_view($type) {
       $class = "language-switcher-{$links->method_id}";
       $variables = array('links' => $links->links, 'attributes' => array('class' => array($class)));
       $block['content'] = theme('links__language_block', $variables);
-      $block['subject'] = t('Languages');
+      $block['default_title'] = t('Languages');
       return $block;
     }
   }
diff --git a/core/modules/node/node.module b/core/modules/node/node.module
index 2dd1b57..d86f79e 100644
--- a/core/modules/node/node.module
+++ b/core/modules/node/node.module
@@ -2154,7 +2154,7 @@ function node_block_view($delta = '') {
 
   switch ($delta) {
     case 'syndicate':
-      $block['subject'] = t('Syndicate');
+      $block['default_title'] = t('Syndicate');
       $block['content'] = array(
         '#theme' => 'feed_icon',
         '#url' => 'rss.xml',
@@ -2164,7 +2164,7 @@ function node_block_view($delta = '') {
 
     case 'recent':
       if (user_access('access content')) {
-        $block['subject'] = t('Recent content');
+        $block['default_title'] = t('Recent content');
         if ($nodes = node_get_recent(variable_get('node_recent_block_count', 10))) {
           $block['content'] = array(
             '#theme' => 'node_recent_block',
diff --git a/core/modules/poll/poll.module b/core/modules/poll/poll.module
index c85f121..c971984 100644
--- a/core/modules/poll/poll.module
+++ b/core/modules/poll/poll.module
@@ -151,7 +151,7 @@ function poll_block_view($delta = '') {
       $poll = node_load($record->nid);
       if ($poll->nid) {
         $poll = poll_block_latest_poll_view($poll);
-        $block['subject'] = t('Poll');
+        $block['default_title'] = t('Poll');
         $block['content'] = $poll->content;
         return $block;
       }
diff --git a/core/modules/search/search.module b/core/modules/search/search.module
index 315ae7a..87a783f 100644
--- a/core/modules/search/search.module
+++ b/core/modules/search/search.module
@@ -149,7 +149,7 @@ function search_block_info() {
  */
 function search_block_view($delta = '') {
   if (user_access('search content')) {
-    $block['subject'] = t('Search');
+    $block['default_title'] = t('Search');
     $block['content'] = drupal_get_form('search_block_form');
     return $block;
   }
diff --git a/core/modules/statistics/statistics.module b/core/modules/statistics/statistics.module
index 8469e52..dcba63f 100644
--- a/core/modules/statistics/statistics.module
+++ b/core/modules/statistics/statistics.module
@@ -370,7 +370,7 @@ function statistics_block_view($delta = '') {
 
     if (count($content)) {
       $block['content'] = $content;
-      $block['subject'] = t('Popular content');
+      $block['default_title'] = t('Popular content');
       return $block;
     }
   }
diff --git a/core/modules/system/system.module b/core/modules/system/system.module
index 4524a49..db43cda 100644
--- a/core/modules/system/system.module
+++ b/core/modules/system/system.module
@@ -2510,22 +2510,22 @@ function system_block_view($delta = '') {
   $block = array();
   switch ($delta) {
     case 'main':
-      $block['subject'] = NULL;
+      $block['default_title'] = NULL;
       $block['content'] = drupal_set_page_content();
       return $block;
     case 'powered-by':
-      $block['subject'] = NULL;
+      $block['default_title'] = NULL;
       $block['content'] = theme('system_powered_by');
       return $block;
     case 'help':
-      $block['subject'] = NULL;
+      $block['default_title'] = NULL;
       $block['content'] = menu_get_active_help();
       return $block;
     default:
       // All system menu blocks.
       $system_menus = menu_list_system_menus();
       if (isset($system_menus[$delta])) {
-        $block['subject'] = t($system_menus[$delta]);
+        $block['default_title'] = t($system_menus[$delta]);
         $block['content'] = menu_tree($delta);
         return $block;
       }
diff --git a/core/modules/user/user.module b/core/modules/user/user.module
index e42002b..8fb09f1 100644
--- a/core/modules/user/user.module
+++ b/core/modules/user/user.module
@@ -841,7 +841,7 @@ function user_block_view($delta = '') {
       // For usability's sake, avoid showing two login forms on one page.
       if (!$user->uid && !(arg(0) == 'user' && !is_numeric(arg(1)))) {
 
-        $block['subject'] = t('User login');
+        $block['default_title'] = t('User login');
         $block['content']['user_login_form'] = drupal_get_form('user_login_block');
       }
       return $block;
@@ -851,7 +851,7 @@ function user_block_view($delta = '') {
         // Retrieve a list of new users who have subsequently accessed the site successfully.
         $items = db_query_range('SELECT uid, name FROM {users} WHERE status <> 0 AND access <> 0 ORDER BY created DESC', 0, variable_get('user_block_whois_new_count', 5))->fetchAll();
 
-        $block['subject'] = t('Who\'s new');
+        $block['default_title'] = t('Who\'s new');
         $block['content'] = array(
           '#theme' => 'item_list__user__new',
           '#items' => array(),
@@ -871,7 +871,7 @@ function user_block_view($delta = '') {
         // rather than u.access because it is much faster.
         $authenticated_count = db_query("SELECT COUNT(DISTINCT s.uid) FROM {sessions} s WHERE s.timestamp >= :timestamp AND s.uid > 0", array(':timestamp' => $interval))->fetchField();
 
-        $block['subject'] = t('Who\'s online');
+        $block['default_title'] = t('Who\'s online');
         $block['content'] = array(
           '#theme' => 'item_list__user__online',
           '#items' => array(),