diff --git a/core/includes/bootstrap.inc b/core/includes/bootstrap.inc
index df0d8c4a6f5..03ed352dc6d 100644
--- a/core/includes/bootstrap.inc
+++ b/core/includes/bootstrap.inc
@@ -2293,7 +2293,7 @@ function _drupal_bootstrap_configuration() {
 
   // Register explicit vendor namespaces.
   $loader->registerNamespaces(array(
-    // All Symfony-borrowed code lives in /core/includes/Symfony.
+    // All Symfony-borrowed code lives in /core/vendor/Symfony.
     'Symfony' => DRUPAL_ROOT . '/core/vendor',
   ));
   // Register the Drupal namespace for classes in core as a fallback.
@@ -2303,7 +2303,7 @@ function _drupal_bootstrap_configuration() {
   // namespace match based on a string comparison. It further allows modules to
   // register/overload namespaces in Drupal core.
   $loader->registerNamespaceFallbacks(array(
-    // All Drupal-namespaced code in core lives in /core/includes/Drupal.
+    // All Drupal-namespaced code in core lives in /core/lib/Drupal.
     'Drupal' => DRUPAL_ROOT . '/core/lib',
   ));
 }
@@ -2653,53 +2653,45 @@ function language_types() {
 }
 
 /**
- * Returns a list of installed languages, indexed by the specified key.
+ * Returns a list of configured languages.
  *
- * @param $field
- *   (optional) The field to index the list with.
+ * @param $only_enabled
+ *   (optional) Whether to return only enabled languages.
  *
  * @return
- *   An associative array, keyed on the values of $field.
- *   - If $field is 'weight' or 'enabled', the array is nested, with the outer
- *     array's values each being associative arrays with language codes as
- *     keys and language objects as values.
- *   - For all other values of $field, the array is only one level deep, and
- *     the array's values are language objects.
+ *   An associative array of languages, keyed by the language code, ordered by
+ *   weight ascending and name ascending.
  */
-function language_list($field = 'langcode') {
+function language_list($only_enabled = FALSE) {
   $languages = &drupal_static(__FUNCTION__);
-  // Init language list
+  // Initialize master language list.
   if (!isset($languages)) {
+    // Initialize local language list caches.
+    $languages = array('all' => array(), 'enabled' => array());
+
+    // Fill in master language list based on current configuration.
     $default = language_default();
     if (language_multilingual() || module_exists('language')) {
-      $languages['langcode'] = db_query('SELECT * FROM {language} ORDER BY weight ASC, name ASC')->fetchAllAssoc('langcode');
+      // Use language module configuration if available.
+      $languages['all'] = db_query('SELECT * FROM {language} ORDER BY weight ASC, name ASC')->fetchAllAssoc('langcode');
     }
     else {
-      // No locale module, so use the default language only.
-      $languages['langcode'][$default->langcode] = $default;
+      // No language module, so use the default language only.
+      $languages['all'][$default->langcode] = $default;
     }
 
-    // Initialize default property so callers have an easy reference and
-    // can save the same object without data loss.
-    foreach ($languages['langcode'] as $langcode => $language) {
-      $languages['langcode'][$langcode]->default = ($langcode == $default->langcode);
-    }
-  }
-
-  // Return the array indexed by the right field
-  if (!isset($languages[$field])) {
-    $languages[$field] = array();
-    foreach ($languages['langcode'] as $lang) {
-      // Some values should be collected into an array
-      if (in_array($field, array('enabled', 'weight'))) {
-        $languages[$field][$lang->$field][$lang->langcode] = $lang;
-      }
-      else {
-        $languages[$field][$lang->$field] = $lang;
+    // Initialize default property so callers have an easy reference and can
+    // save the same object without data loss. Also fill in the filtered list
+    // of enabled languages only.
+    foreach ($languages['all'] as $langcode => $language) {
+      $languages['all'][$langcode]->default = ($langcode == $default->langcode);
+      if ($language->enabled) {
+        $languages['enabled'][$langcode] = $languages['all'][$langcode];
       }
     }
   }
-  return $languages[$field];
+
+  return $only_enabled ? $languages['enabled'] : $languages['all'];
 }
 
 /**
@@ -3205,29 +3197,29 @@ function registry_update() {
  *
  * Example:
  * @code
- * function language_list($field = 'langcode') {
- *   $languages = &drupal_static(__FUNCTION__);
- *   if (!isset($languages)) {
+ * function example_list($field = 'default') {
+ *   $examples = &drupal_static(__FUNCTION__);
+ *   if (!isset($examples)) {
  *     // If this function is being called for the first time after a reset,
  *     // query the database and execute any other code needed to retrieve
- *     // information about the supported languages.
+ *     // information.
  *     ...
  *   }
- *   if (!isset($languages[$field])) {
+ *   if (!isset($examples[$field])) {
  *     // If this function is being called for the first time for a particular
  *     // index field, then execute code needed to index the information already
- *     // available in $languages by the desired field.
+ *     // available in $examples by the desired field.
  *     ...
  *   }
  *   // Subsequent invocations of this function for a particular index field
  *   // skip the above two code blocks and quickly return the already indexed
  *   // information.
- *   return $languages[$field];
+ *   return $examples[$field];
  * }
- * function locale_translate_overview_screen() {
- *   // When building the content for the translations overview page, make
- *   // sure to get completely fresh information about the supported languages.
- *   drupal_static_reset('language_list');
+ * function examples_admin_overview() {
+ *   // When building the content for the overview page, make sure to get
+ *   // completely fresh information.
+ *   drupal_static_reset('example_list');
  *   ...
  * }
  * @endcode
diff --git a/core/includes/language.inc b/core/includes/language.inc
index d1d2eaf1bbc..46280532597 100644
--- a/core/includes/language.inc
+++ b/core/includes/language.inc
@@ -329,9 +329,8 @@ function language_provider_invoke($provider_id, $provider = NULL) {
   if (!isset($results[$provider_id])) {
     global $user;
 
-    // Get languages grouped by status and select only the enabled ones.
-    $languages = language_list('enabled');
-    $languages = $languages[1];
+    // Get the enabled languages only.
+    $languages = language_list(TRUE);
 
     if (!isset($provider)) {
       $providers = language_negotiation_info();
@@ -454,17 +453,8 @@ function language_fallback_get_candidates($type = LANGUAGE_TYPE_CONTENT) {
   $fallback_candidates = &drupal_static(__FUNCTION__);
 
   if (!isset($fallback_candidates)) {
-    $fallback_candidates = array();
-
-    // Get languages ordered by weight.
-    // Use array keys to avoid duplicated entries.
-    foreach (language_list('weight') as $languages) {
-      foreach ($languages as $language) {
-        $fallback_candidates[$language->langcode] = NULL;
-      }
-    }
-
-    $fallback_candidates = array_keys($fallback_candidates);
+    // Get languages ordered by weight, add LANGUAGE_NONE as the last one.
+    $fallback_candidates = array_keys(language_list());
     $fallback_candidates[] = LANGUAGE_NONE;
 
     // Let other modules hook in and add/change candidates.
diff --git a/core/includes/locale.inc b/core/includes/locale.inc
index a73ccc25a5b..e2a79b62385 100644
--- a/core/includes/locale.inc
+++ b/core/includes/locale.inc
@@ -349,14 +349,16 @@ function locale_language_url_fallback($language = NULL, $language_type = LANGUAG
 }
 
 /**
- * Return the URL language switcher block. Translation links may be provided by
- * other modules.
+ * Return links for the URL language switcher block.
+ *
+ * Translation links may be provided by other modules.
  */
 function locale_language_switcher_url($type, $path) {
-  $languages = language_list('enabled');
+  // Get the enabled languages only.
+  $languages = language_list(TRUE);
   $links = array();
 
-  foreach ($languages[1] as $language) {
+  foreach ($languages as $language) {
     $links[$language->langcode] = array(
       'href'       => $path,
       'title'      => $language->name,
@@ -377,13 +379,14 @@ function locale_language_switcher_session($type, $path) {
   $param = variable_get('locale_language_negotiation_session_param', 'language');
   $language_query = isset($_SESSION[$param]) ? $_SESSION[$param] : $GLOBALS[$type]->langcode;
 
-  $languages = language_list('enabled');
+  // Get the enabled languages only.
+  $languages = language_list(TRUE);
   $links = array();
 
   $query = $_GET;
   unset($query['q']);
 
-  foreach ($languages[1] as $language) {
+  foreach ($languages as $language) {
     $langcode = $language->langcode;
     $links[$langcode] = array(
       'href'       => $path,
@@ -413,8 +416,9 @@ function locale_language_url_rewrite_url(&$path, &$options) {
   $languages = &$drupal_static_fast['languages'];
 
   if (!isset($languages)) {
-    $languages = language_list('enabled');
-    $languages = array_flip(array_keys($languages[1]));
+    // Get the enabled languages only.
+    $languages = language_list(TRUE);
+    $languages = array_flip(array_keys($languages));
   }
 
   // Language can be passed as an option, or we go for current URL language.
@@ -488,8 +492,8 @@ function locale_language_url_rewrite_session(&$path, &$options) {
   if (!isset($query_rewrite)) {
     global $user;
     if (!$user->uid) {
-      $languages = language_list('enabled');
-      $languages = $languages[1];
+      // Get the enabled languages only.
+      $languages = language_list(TRUE);
       $query_param = check_plain(variable_get('locale_language_negotiation_session_param', 'language'));
       $query_value = isset($_GET[$query_param]) ? check_plain($_GET[$query_param]) : NULL;
       $query_rewrite = isset($languages[$query_value]) && language_negotiation_get_any(LOCALE_LANGUAGE_NEGOTIATION_SESSION);
diff --git a/core/modules/dashboard/dashboard-rtl.css b/core/modules/dashboard/dashboard-rtl.css
index cfccfa0310a..8d3d0edd05c 100644
--- a/core/modules/dashboard/dashboard-rtl.css
+++ b/core/modules/dashboard/dashboard-rtl.css
@@ -1,3 +1,8 @@
+/**
+ * @file
+ * Right-to-left specific stylesheet for the Dashboard module.
+ */
+
 #dashboard div.dashboard-region {
   float: right;
 }
diff --git a/core/modules/dashboard/dashboard.api.php b/core/modules/dashboard/dashboard.api.php
index 00bfde5a30a..623dd30abe3 100644
--- a/core/modules/dashboard/dashboard.api.php
+++ b/core/modules/dashboard/dashboard.api.php
@@ -11,7 +11,7 @@
  */
 
 /**
- * Adds regions to the dashboard.
+ * Add regions to the dashboard.
  *
  * @return
  *   An array whose keys are the names of the dashboard regions and whose
diff --git a/core/modules/dashboard/dashboard.css b/core/modules/dashboard/dashboard.css
index 9996ba9d77d..e94964091cb 100644
--- a/core/modules/dashboard/dashboard.css
+++ b/core/modules/dashboard/dashboard.css
@@ -1,3 +1,8 @@
+/**
+ * @file
+ * Stylesheet for the Dashboard module.
+ */
+
 #dashboard div.dashboard-region {
   float: left;
   min-height: 1px;
diff --git a/core/modules/dashboard/dashboard.js b/core/modules/dashboard/dashboard.js
index ebecbf65a44..ca2a3b5dea3 100644
--- a/core/modules/dashboard/dashboard.js
+++ b/core/modules/dashboard/dashboard.js
@@ -1,7 +1,12 @@
+/**
+ * @file
+ * Attaches behaviors for the Dashboard module.
+ */
+
 (function ($) {
 
 /**
- * Implementation of Drupal.behaviors for dashboard.
+ * Implements Drupal.behaviors for the Dashboard module.
  */
 Drupal.behaviors.dashboard = {
     attach: function (context, settings) {
@@ -39,7 +44,7 @@ Drupal.behaviors.dashboard = {
   },
 
   /**
-   * Enter "customize" mode by displaying disabled blocks.
+   * Enters "customize" mode by displaying disabled blocks.
    */
   enterCustomizeMode: function () {
     $('#dashboard').addClass('customize-mode customize-inactive');
@@ -51,7 +56,7 @@ Drupal.behaviors.dashboard = {
   },
 
   /**
-   * Exit "customize" mode by simply forcing a page refresh.
+   * Exits "customize" mode by simply forcing a page refresh.
    */
   exitCustomizeMode: function () {
     $('#dashboard').removeClass('customize-mode customize-inactive');
@@ -60,7 +65,7 @@ Drupal.behaviors.dashboard = {
   },
 
   /**
-   * Helper for enterCustomizeMode; sets up drag-and-drop and close button.
+   * Sets up the drag-and-drop behavior and the 'close' button.
    */
   setupDrawer: function () {
     $('div.customize .canvas-content input').click(Drupal.behaviors.dashboard.exitCustomizeMode);
@@ -84,7 +89,7 @@ Drupal.behaviors.dashboard = {
   },
 
   /**
-   * While dragging, make the block appear as a disabled block
+   * Makes the block appear as a disabled block while dragging.
    *
    * This function is called on the jQuery UI Sortable "start" event.
    *
@@ -104,8 +109,7 @@ Drupal.behaviors.dashboard = {
   },
 
   /**
-   * While dragging, adapt block's width to the width of the region it is moved
-   * into.
+   * Adapts block's width to the region it is moved into while dragging.
    *
    * This function is called on the jQuery UI Sortable "over" event.
    *
@@ -127,8 +131,7 @@ Drupal.behaviors.dashboard = {
   },
 
   /**
-   * While dragging, adapt block's position to stay connected with the position
-   * of the mouse pointer.
+   * Adapts a block's position to stay connected with the mouse pointer.
    *
    * This function is called on the jQuery UI Sortable "sort" event.
    *
@@ -146,7 +149,7 @@ Drupal.behaviors.dashboard = {
   },
 
   /**
-   * Send block order to the server, and expand previously disabled blocks.
+   * Sends block order to the server, and expands previously disabled blocks.
    *
    * This function is called on the jQuery UI Sortable "update" event.
    *
@@ -198,8 +201,10 @@ Drupal.behaviors.dashboard = {
   },
 
   /**
-   * Return the current order of the blocks in each of the sortable regions,
-   * in query string format.
+   * Returns the current order of the blocks in each of the sortable regions.
+   *
+   * @return
+   *   The current order of the blocks, in query string format.
    */
   getOrder: function () {
     var order = [];
diff --git a/core/modules/dashboard/dashboard.module b/core/modules/dashboard/dashboard.module
index 115bc8fafa6..1891db59ea4 100644
--- a/core/modules/dashboard/dashboard.module
+++ b/core/modules/dashboard/dashboard.module
@@ -1,5 +1,10 @@
 <?php
 
+/**
+ * @file
+ * Provides a dashboard page in the administrative interface.
+ */
+
 /**
  * Implements hook_help().
  */
@@ -263,10 +268,12 @@ function dashboard_forms() {
 }
 
 /**
- * Dashboard page callback.
+ * Page callback: Displays the dashboard.
  *
  * @param $launch_customize
  *   Whether to launch in customization mode right away. TRUE or FALSE.
+ *
+ * @see dashboard_menu()
  */
 function dashboard_admin($launch_customize = FALSE) {
   $js_settings = array(
@@ -298,11 +305,12 @@ function dashboard_admin($launch_customize = FALSE) {
 }
 
 /**
- * Menu page callback: builds the page for administering dashboard blocks.
+ * Page callback: Builds the page for administering dashboard blocks.
  *
  * This page reuses the Block module's administration form but limits editing
  * to blocks that are available to appear on the dashboard.
  *
+ * @see dashboard_menu()
  * @see block_admin_display()
  * @see block_admin_display_form()
  * @see dashboard_form_dashboard_admin_display_form_alter()
@@ -454,7 +462,7 @@ function dashboard_is_visible() {
 }
 
 /**
- * Return an array of dashboard region descriptions, keyed by region name.
+ * Returns an array of dashboard region descriptions, keyed by region name.
  */
 function dashboard_region_descriptions() {
   $regions = module_invoke_all('dashboard_regions');
@@ -463,7 +471,7 @@ function dashboard_region_descriptions() {
 }
 
 /**
- * Return an array of dashboard region names.
+ * Returns an array of dashboard region names.
  */
 function dashboard_regions() {
   $regions = &drupal_static(__FUNCTION__);
@@ -485,7 +493,9 @@ function dashboard_dashboard_regions() {
 }
 
 /**
- * Ajax callback to show disabled blocks in the dashboard customization mode.
+ * Ajax callback: Shows disabled blocks in the dashboard customization mode.
+ *
+ * @see dashboard_menu()
  */
 function dashboard_show_disabled() {
   global $theme_key;
@@ -506,12 +516,14 @@ function dashboard_show_disabled() {
 }
 
 /**
- * Ajax callback to display the rendered contents of a specific block.
+ * Ajax callback: Displays the rendered contents of a specific block.
  *
  * @param $module
  *   The block's module name.
  * @param $delta
  *   The block's delta.
+ *
+ * @see dashboard_menu()
  */
 function dashboard_show_block_content($module, $delta) {
   drupal_theme_initialize();
@@ -533,7 +545,7 @@ function dashboard_show_block_content($module, $delta) {
 }
 
 /**
- * Set the new weight of each region according to the drag-and-drop order.
+ * Sets the new weight of each region according to the drag-and-drop order.
  */
 function dashboard_update() {
   drupal_theme_initialize();
@@ -630,7 +642,7 @@ function theme_dashboard_region($variables) {
 }
 
 /**
- * Returns HTML for a set of disabled blocks, for display in dashboard customization mode.
+ * Returns HTML for disabled blocks, for use in dashboard customization mode.
  *
  * @param $variables
  *   An associative array containing:
@@ -652,7 +664,7 @@ function theme_dashboard_disabled_blocks($variables) {
 }
 
 /**
- * Returns HTML for a disabled block, for display in dashboard customization mode.
+ * Returns HTML for a disabled block, for use in dashboard customization mode.
  *
  * @param $variables
  *   An associative array containing:
diff --git a/core/modules/dashboard/dashboard.test b/core/modules/dashboard/dashboard.test
index 7cb93f9f17f..56bdb132d22 100644
--- a/core/modules/dashboard/dashboard.test
+++ b/core/modules/dashboard/dashboard.test
@@ -5,6 +5,9 @@
  * Tests for dashboard.module.
  */
 
+/**
+ * Tests the Dashboard module blocks.
+ */
 class DashboardBlocksTestCase extends DrupalWebTestCase {
   public static function getInfo() {
     return array(
@@ -33,7 +36,7 @@ class DashboardBlocksTestCase extends DrupalWebTestCase {
   }
 
   /**
-   * Test adding a block to the dashboard and checking access to it.
+   * Tests adding a block to the dashboard and checking access to it.
    */
   function testDashboardAccess() {
     // Add a new custom block to a dashboard region.
@@ -58,7 +61,7 @@ class DashboardBlocksTestCase extends DrupalWebTestCase {
   }
 
   /**
-   * Test that dashboard regions are displayed or hidden properly.
+   * Tests that dashboard regions are displayed or hidden properly.
    */
   function testDashboardRegions() {
     $dashboard_regions = dashboard_region_descriptions();
@@ -80,8 +83,7 @@ class DashboardBlocksTestCase extends DrupalWebTestCase {
   }
 
   /**
-   * Test that the dashboard module can be disabled and enabled again,
-   * retaining its blocks.
+   * Tests that the dashboard module can be re-enabled, retaining its blocks.
    */
   function testDisableEnable() {
     // Add a new custom block to a dashboard region.
@@ -113,8 +115,7 @@ class DashboardBlocksTestCase extends DrupalWebTestCase {
   }
 
   /**
-   * Test that defining a block with ['properties']['administrative'] = TRUE
-   * adds it as an available block for the dashboard.
+   * Tests that administrative blocks are available for the dashboard.
    */
   function testBlockAvailability() {
     // Test "Recent comments", which should be available (defined as
diff --git a/core/modules/language/language.test b/core/modules/language/language.test
index 435548dfe12..0a599379ca3 100644
--- a/core/modules/language/language.test
+++ b/core/modules/language/language.test
@@ -122,8 +122,8 @@ class LanguageListTest extends DrupalWebTestCase {
     $this->assertResponse(404, t('Language no longer found.'));
     // Make sure the "language_count" variable has been updated correctly.
     drupal_static_reset('language_list');
-    $enabled = language_list('enabled');
-    $this->assertEqual(variable_get('language_count', 1), count($enabled[1]), t('Language count is correct.'));
+    $enabled_languages = language_list(TRUE);
+    $this->assertEqual(variable_get('language_count', 1), count($enabled_languages), t('Language count is correct.'));
     // Delete a disabled language.
     // Disable an enabled language.
     $edit = array(
@@ -133,7 +133,7 @@ class LanguageListTest extends DrupalWebTestCase {
     $this->assertNoFieldChecked('edit-languages-fr-enabled', t('French language disabled.'));
     // Get the count of enabled languages.
     drupal_static_reset('language_list');
-    $enabled = language_list('enabled');
+    $enabled_languages = language_list(TRUE);
     // Delete the disabled language.
     $this->drupalPost('admin/config/regional/language/delete/fr', array(), t('Delete'));
     // We need raw here because %language and %langcode will add HTML.
@@ -144,7 +144,7 @@ class LanguageListTest extends DrupalWebTestCase {
     $this->drupalGet('admin/config/regional/language/delete/fr');
     $this->assertResponse(404, t('Language no longer found.'));
     // Make sure the "language_count" variable has not changed.
-    $this->assertEqual(variable_get('language_count', 1), count($enabled[1]), t('Language count is correct.'));
+    $this->assertEqual(variable_get('language_count', 1), count($enabled_languages), t('Language count is correct.'));
 
     // Ensure we can delete the English language. Right now English is the only
     // language so we must add a new language and make it the default before
diff --git a/core/modules/locale/locale.admin.inc b/core/modules/locale/locale.admin.inc
index 26165f87465..c0a91370e3d 100644
--- a/core/modules/locale/locale.admin.inc
+++ b/core/modules/locale/locale.admin.inc
@@ -256,10 +256,11 @@ function locale_language_providers_url_form($form, &$form_state) {
     ),
   );
 
-  $languages = language_list('enabled');
+  // Get the enabled languages only.
+  $languages = language_list(TRUE);
   $prefixes = locale_language_negotiation_url_prefixes();
   $domains = locale_language_negotiation_url_domains();
-  foreach ($languages[1] as $langcode => $language) {
+  foreach ($languages as $langcode => $language) {
     $form['prefix'][$langcode] = array(
       '#type' => 'textfield',
       '#title' => t('%language (%langcode) path prefix', array('%language' => $language->name, '%langcode' => $language->langcode)),
@@ -292,40 +293,41 @@ function locale_language_providers_url_form($form, &$form_state) {
  * the prefix and domain are only blank for the default.
  */
 function locale_language_providers_url_form_validate($form, &$form_state) {
-  $languages = locale_language_list();
+  // Get the enabled languages only.
+  $languages = language_list(TRUE);
   $default = language_default();
 
   // Count repeated values for uniqueness check.
   $count = array_count_values($form_state['values']['prefix']);
-  foreach ($languages as $langcode => $name) {
+  foreach ($languages as $langcode => $language) {
     $value = $form_state['values']['prefix'][$langcode];
 
     if ($value === '') {
-      if ($default->langcode != $langcode && $form_state['values']['locale_language_negotiation_url_part'] == LOCALE_LANGUAGE_NEGOTIATION_URL_PREFIX) {
+      if (!$language->default && $form_state['values']['locale_language_negotiation_url_part'] == LOCALE_LANGUAGE_NEGOTIATION_URL_PREFIX) {
         // Validation error if the prefix is blank for a non-default language, and value is for selected negotiation type.
         form_error($form['prefix'][$langcode], t('The prefix may only be left blank for the default language.'));
       }
     }
     else if (isset($count[$value]) && $count[$value] > 1) {
       // Validation error if there are two languages with the same domain/prefix.
-      form_error($form['prefix'][$langcode], t('The prefix for %language, %value, is not unique.', array( '%language' => $name, '%value' => $value )));
+      form_error($form['prefix'][$langcode], t('The prefix for %language, %value, is not unique.', array('%language' => $language->name, '%value' => $value)));
     }
   }
 
   // Count repeated values for uniqueness check.
   $count = array_count_values($form_state['values']['domain']);
-  foreach ($languages as $langcode => $name) {
+  foreach ($languages as $langcode => $language) {
     $value = $form_state['values']['domain'][$langcode];
 
     if ($value === '') {
-      if ($default->langcode != $langcode && $form_state['values']['locale_language_negotiation_url_part'] == LOCALE_LANGUAGE_NEGOTIATION_URL_DOMAIN) {
+      if (!$language->default && $form_state['values']['locale_language_negotiation_url_part'] == LOCALE_LANGUAGE_NEGOTIATION_URL_DOMAIN) {
         // Validation error if the domain is blank for a non-default language, and value is for selected negotiation type.
         form_error($form['domain'][$langcode], t('The domain may only be left blank for the default language.'));
       }
     }
     else if (isset($count[$value]) && $count[$value] > 1) {
       // Validation error if there are two languages with the same domain/domain.
-      form_error($form['domain'][$langcode], t('The domain for %language, %value, is not unique.', array( '%language' => $name, '%value' => $value )));
+      form_error($form['domain'][$langcode], t('The domain for %language, %value, is not unique.', array('%language' => $language->name, '%value' => $value)));
     }
   }
 }
@@ -405,12 +407,12 @@ function locale_date_format_language_overview_page() {
     array('data' => t('Operations'), 'colspan' => '2'),
   );
 
-  // Get list of languages.
-  $languages = locale_language_list();
+  // Get the enabled languages only.
+  $languages = language_list(TRUE);
 
-  foreach ($languages as $langcode => $info) {
+  foreach ($languages as $langcode => $language) {
     $row = array();
-    $row[] = $languages[$langcode];
+    $row[] = $language->name;
     $row[] = l(t('edit'), 'admin/config/regional/date-time/locale/' . $langcode . '/edit');
     $row[] = l(t('reset'), 'admin/config/regional/date-time/locale/' . $langcode . '/reset');
     $rows[] = $row;
@@ -423,14 +425,11 @@ function locale_date_format_language_overview_page() {
  * Provide date localization configuration options to users.
  */
 function locale_date_format_form($form, &$form_state, $langcode) {
-  $languages = locale_language_list();
-  $language_name = $languages[$langcode];
-
   // Display the current language name.
   $form['language'] = array(
     '#type' => 'item',
     '#title' => t('Language'),
-    '#markup' => check_plain($language_name),
+    '#markup' => language_load($langcode)->name,
     '#weight' => -10,
   );
   $form['langcode'] = array(
@@ -509,9 +508,8 @@ function locale_date_format_form_submit($form, &$form_state) {
  */
 function locale_date_format_reset_form($form, &$form_state, $langcode) {
   $form['langcode'] = array('#type' => 'value', '#value' => $langcode);
-  $languages = language_list();
   return confirm_form($form,
-    t('Are you sure you want to reset the date formats for %language to the global defaults?', array('%language' => $languages[$langcode]->name)),
+    t('Are you sure you want to reset the date formats for %language to the global defaults?', array('%language' => language_load($langcode)->name)),
     'admin/config/regional/date-time/locale',
     t('Resetting will remove all localized date formats for this language. This action cannot be undone.'),
     t('Reset'), t('Cancel'));
diff --git a/core/modules/locale/locale.bulk.inc b/core/modules/locale/locale.bulk.inc
index 7982a980346..a4982e13e1a 100644
--- a/core/modules/locale/locale.bulk.inc
+++ b/core/modules/locale/locale.bulk.inc
@@ -11,24 +11,32 @@ include_once DRUPAL_ROOT . '/core/includes/gettext.inc';
  * User interface for the translation import screen.
  */
 function locale_translate_import_form($form, &$form_state) {
-  // Get all languages, except English
   drupal_static_reset('language_list');
-  $names = locale_language_list('name');
-  if (!locale_translate_english()) {
-    unset($names['en']);
+  $languages = language_list(TRUE);
+
+  // Initialize a language list to the ones available, including English if we
+  // are to translate Drupal to English as well.
+  $existing_languages = array();
+  foreach ($languages as $langcode => $language) {
+    if ($langcode != 'en' || locale_translate_english()) {
+      $existing_languages[$langcode] = $language->name;
+    }
   }
 
+  // If we have no languages available, present the list of predefined languages
+  // only. If we do have already added languages, set up two option groups with
+  // the list of existing and then predefined languages.
   form_load_include($form_state, 'inc', 'language', 'language.admin');
-  if (!count($names)) {
-    $languages = language_admin_predefined_list();
-    $default = key($languages);
+  if (empty($existing_languages)) {
+    $language_options = language_admin_predefined_list();
+    $default = key($language_options);
   }
   else {
-    $languages = array(
-      t('Already added languages') => $names,
+    $default = key($existing_languages);
+    $language_options = array(
+      t('Already added languages') => $existing_languages,
       t('Languages not yet added') => language_admin_predefined_list()
     );
-    $default = key($names);
   }
 
   $form['import'] = array('#type' => 'fieldset',
@@ -41,7 +49,7 @@ function locale_translate_import_form($form, &$form_state) {
   );
   $form['import']['langcode'] = array('#type' => 'select',
     '#title' => t('Import into'),
-    '#options' => $languages,
+    '#options' => $language_options,
     '#default_value' => $default,
     '#description' => t('Choose the language you want to add strings into. If you choose a language which is not yet set up, it will be added.'),
   );
@@ -101,16 +109,20 @@ function locale_translate_import_form_submit($form, &$form_state) {
  * User interface for the translation export screen.
  */
 function locale_translate_export_screen() {
-  // Get all languages, except English
+  // Get all enabled languages, except English, if we should not translate that.
   drupal_static_reset('language_list');
-  $names = locale_language_list('name');
-  if (!locale_translate_english()) {
-    unset($names['en']);
+  $languages = language_list(TRUE);
+  $language_options = array();
+  foreach ($languages as $langcode => $language) {
+    if ($langcode != 'en' || locale_translate_english()) {
+      $language_options[$langcode] = $language->name;
+    }
   }
+
   $output = '';
   // Offer translation export if any language is set up.
-  if (count($names)) {
-    $elements = drupal_get_form('locale_translate_export_po_form', $names);
+  if (!empty($language_options)) {
+    $elements = drupal_get_form('locale_translate_export_po_form', $language_options);
     $output = drupal_render($elements);
   }
   $elements = drupal_get_form('locale_translate_export_pot_form');
diff --git a/core/modules/locale/locale.module b/core/modules/locale/locale.module
index 9330df1134e..6b189889b50 100644
--- a/core/modules/locale/locale.module
+++ b/core/modules/locale/locale.module
@@ -219,8 +219,8 @@ function locale_permission() {
  */
 function locale_language_selector_form($user) {
   global $language;
-  $languages = language_list('enabled');
-  $languages = $languages[1];
+  // Get list of enabled languages only.
+  $languages = language_list(TRUE);
 
   // If the user is being created, we set the user language to the page language.
   $user_preferred_language = $user->uid ? user_preferred_language($user) : $language;
@@ -296,11 +296,16 @@ function locale_form_alter(&$form, &$form_state, $form_id) {
  */
 function locale_form_node_form_alter(&$form, &$form_state) {
   if (isset($form['#node']->type) && locale_multilingual_node_type($form['#node']->type)) {
+    $languages = language_list(TRUE);
+    $language_options = array(LANGUAGE_NONE => t('Language neutral'));
+    foreach ($languages as $langcode => $language) {
+      $language_options[$langcode] = $language->name;
+    }
     $form['language'] = array(
       '#type' => 'select',
       '#title' => t('Language'),
       '#default_value' => (isset($form['#node']->language) ? $form['#node']->language : ''),
-      '#options' => array(LANGUAGE_NONE => t('Language neutral')) + locale_language_list('name'),
+      '#options' => $language_options,
     );
   }
   // Node type without language selector: assign the default for new nodes
@@ -764,37 +769,12 @@ function locale_get_plural($count, $langcode = NULL) {
 
 
 /**
- * Returns a language name
+ * Returns a language name.
  */
-function locale_language_name($lang) {
-  $list = &drupal_static(__FUNCTION__);
-  if (!isset($list)) {
-    $list = locale_language_list();
-  }
-  return ($lang && isset($list[$lang])) ? $list[$lang] : t('All');
-}
-
-/**
- * Returns array of language names
- *
- * @param $field
- *   Name of language object field.
- * @param $all
- *   Boolean to return all languages or only enabled ones
- */
-function locale_language_list($field = 'name', $all = FALSE) {
-  if ($all) {
-    $languages = language_list();
-  }
-  else {
-    $languages = language_list('enabled');
-    $languages = $languages[1];
-  }
-  $list = array();
-  foreach ($languages as $language) {
-    $list[$language->langcode] = $language->$field;
-  }
-  return $list;
+function locale_language_name($langcode) {
+  // Consider enabled languages only.
+  $languages = language_list(TRUE);
+  return ($langcode && isset($languages[$langcode])) ? $languages[$langcode]->name : t('All');
 }
 
 /**
diff --git a/core/modules/locale/locale.pages.inc b/core/modules/locale/locale.pages.inc
index ef843ec1fab..e41bae59d4b 100644
--- a/core/modules/locale/locale.pages.inc
+++ b/core/modules/locale/locale.pages.inc
@@ -152,9 +152,12 @@ function locale_translation_filters() {
 
   // Get all languages, except English
   drupal_static_reset('language_list');
-  $languages = locale_language_list('name');
-  if (!locale_translate_english()) {
-    unset($languages['en']);
+  $languages = language_list(TRUE);
+  $language_options = array();
+  foreach ($languages as $langcode => $language) {
+    if ($langcode != 'en' || locale_translate_english()) {
+      $language_options[$langcode] = $language->name;
+    }
   }
 
   $filters['string'] = array(
@@ -164,7 +167,7 @@ function locale_translation_filters() {
 
   $filters['language'] = array(
     'title' => t('Language'),
-    'options' => array_merge(array('all' => t('All languages'), LANGUAGE_SYSTEM => t('System (English)')), $languages),
+    'options' => array_merge(array('all' => t('All languages'), LANGUAGE_SYSTEM => t('System (English)')), $language_options),
   );
 
   $filters['translation'] = array(
diff --git a/core/modules/locale/locale.test b/core/modules/locale/locale.test
index fae4688b272..f102d4bdf5a 100644
--- a/core/modules/locale/locale.test
+++ b/core/modules/locale/locale.test
@@ -2032,8 +2032,8 @@ class LocaleUILanguageNegotiationTest extends DrupalWebTestCase {
     // is for some reason not found when doing translate search. This might
     // be some bug.
     drupal_static_reset('language_list');
-    $languages = language_list('enabled');
-    variable_set('language_default', $languages[1]['vi']);
+    $languages = language_list(TRUE);
+    variable_set('language_default', $languages['vi']);
     // First visit this page to make sure our target string is searchable.
     $this->drupalGet('admin/config');
     // Now the t()'ed string is in db so switch the language back to default.
diff --git a/core/modules/node/node.admin.inc b/core/modules/node/node.admin.inc
index d8caa94f610..b5b2075cdc3 100644
--- a/core/modules/node/node.admin.inc
+++ b/core/modules/node/node.admin.inc
@@ -106,14 +106,18 @@ function node_filters() {
     ) + node_type_get_names(),
   );
 
-  // Language filter if there is a list of languages
-  if ($languages = module_invoke('locale', 'language_list')) {
-    $languages = array(LANGUAGE_NONE => t('Language neutral')) + $languages;
+  // Language filter if the site is multilingual.
+  if (language_multilingual()) {
+    $languages = language_list(TRUE);
+    $language_options = array(LANGUAGE_NONE => t('Language neutral'));
+    foreach ($languages as $langcode => $language) {
+      $language_options[$langcode] = $language->name;
+    }
     $filters['language'] = array(
       'title' => t('language'),
       'options' => array(
         '[any]' => t('any'),
-      ) + $languages,
+      ) + $language_options,
     );
   }
   return $filters;
diff --git a/core/modules/openid/openid.module b/core/modules/openid/openid.module
index 1180114481e..edd73d39cc1 100644
--- a/core/modules/openid/openid.module
+++ b/core/modules/openid/openid.module
@@ -258,8 +258,7 @@ function openid_form_user_register_form_alter(&$form, &$form_state) {
         $candidate_languages[] = $parts[0] . '-' . $parts[2];
         $candidate_languages[] = $parts[0] . '-' . $parts[1] . '-' . $parts[2];
       }
-      $all_languages = language_list('enabled');
-      $enabled_languages = $all_languages[1];
+      $enabled_languages = language_list(TRUE);
       // Iterate over the generated permutations starting with the longest (most
       // specific) strings.
       foreach (array_reverse($candidate_languages) as $candidate_language) {
diff --git a/core/modules/path/path.admin.inc b/core/modules/path/path.admin.inc
index 0ad3ab56ff1..4bca34ad478 100644
--- a/core/modules/path/path.admin.inc
+++ b/core/modules/path/path.admin.inc
@@ -132,10 +132,16 @@ function path_admin_form($form, &$form_state, $path = array('source' => '', 'ali
 
   // A hidden value unless locale module is enabled.
   if (module_exists('locale')) {
+    $languages = language_list(TRUE);
+    $language_options = array(LANGUAGE_NONE => t('All languages'));
+    foreach ($languages as $langcode => $language) {
+      $language_options[$langcode] = $language->name;
+    }
+
     $form['langcode'] = array(
       '#type' => 'select',
       '#title' => t('Language'),
-      '#options' => array(LANGUAGE_NONE => t('All languages')) + locale_language_list('name'),
+      '#options' => $language_options,
       '#default_value' => $path['langcode'],
       '#weight' => -10,
       '#description' => t('A path alias set for a specific language will always be used when displaying this page in that language, and takes precedence over path aliases set for <em>All languages</em>.'),
diff --git a/core/modules/system/system.module b/core/modules/system/system.module
index 5fb47add426..a5bfd1023d0 100644
--- a/core/modules/system/system.module
+++ b/core/modules/system/system.module
@@ -3908,10 +3908,7 @@ function system_date_format_save($date_format, $dfid = 0) {
   }
 
   // Retrieve an array of language objects for enabled languages.
-  $languages = language_list('enabled');
-  // This list is keyed off the value of $language->enabled; we want the ones
-  // that are enabled (value of 1).
-  $languages = $languages[1];
+  $languages = language_list(TRUE);
 
   $locale_format = array();
   $locale_format['type'] = $date_format['type'];
diff --git a/core/modules/taxonomy/taxonomy.module b/core/modules/taxonomy/taxonomy.module
index 338638f6c8b..606abfc017e 100644
--- a/core/modules/taxonomy/taxonomy.module
+++ b/core/modules/taxonomy/taxonomy.module
@@ -1048,9 +1048,9 @@ function taxonomy_get_tree($vid, $parent = 0, $max_depth = NULL, $load_entities
           break;
         }
         $term = $load_entities ? $term_entities[$child] : $terms[$vid][$child];
-        if (count($parents[$vid][$term->tid]) > 1) {
-          // We have a term with multi parents here. Clone the term,
-          // so that the depth attribute remains correct.
+        if (isset($parents[$vid][$term->tid])) {
+          // Clone the term so that the depth attribute remains correct
+          // in the event of multiple parents.
           $term = clone $term;
         }
         $term->depth = $depth;
diff --git a/core/modules/taxonomy/taxonomy.test b/core/modules/taxonomy/taxonomy.test
index a7f7bd9d6be..aa3c20993a6 100644
--- a/core/modules/taxonomy/taxonomy.test
+++ b/core/modules/taxonomy/taxonomy.test
@@ -416,6 +416,60 @@ class TaxonomyTermUnitTest extends TaxonomyWebTestCase {
     // Delete an invalid term. Should not throw any notices.
     taxonomy_term_delete(42);
   }
+
+  /**
+   * Test a taxonomy with terms that have multiple parents of different depths.
+   */
+  function testTaxonomyVocabularyTree() {
+    // Create a new vocabulary with 6 terms.
+    $vocabulary = $this->createVocabulary();
+    $term = array();
+    for ($i = 0; $i < 6; $i++) {
+      $term[$i] = $this->createTerm($vocabulary);
+    }
+
+    // $term[2] is a child of 1 and 5.
+    $term[2]->parent = array($term[1]->tid, $term[5]->tid);
+    taxonomy_term_save($term[2]);
+    // $term[3] is a child of 2.
+    $term[3]->parent = array($term[2]->tid);
+    taxonomy_term_save($term[3]);
+    // $term[5] is a child of 4.
+    $term[5]->parent = array($term[4]->tid);
+    taxonomy_term_save($term[5]);
+
+    /**
+     * Expected tree:
+     * term[0] | depth: 0
+     * term[1] | depth: 0
+     * -- term[2] | depth: 1
+     * ---- term[3] | depth: 2
+     * term[4] | depth: 0
+     * -- term[5] | depth: 1
+     * ---- term[2] | depth: 2
+     * ------ term[3] | depth: 3
+     */
+
+    // Count $term[1] parents with $max_depth = 1.
+    $tree = taxonomy_get_tree($vocabulary->vid, $term[1]->tid, 1);
+    $this->assertEqual(1, count($tree), 'We have one parent with depth 1.');
+
+    // Count all vocabulary tree elements.
+    $tree = taxonomy_get_tree($vocabulary->vid);
+    $this->assertEqual(8, count($tree), 'We have all vocabulary tree elements.');
+
+    // Count elements in every tree depth.
+    foreach($tree as $element) {
+      if (!isset($depth_count[$element->depth])) {
+        $depth_count[$element->depth] = 0;
+      }
+      $depth_count[$element->depth]++;
+    }
+    $this->assertEqual(3, $depth_count[0], 'Three elements in taxonomy tree depth 0.');
+    $this->assertEqual(2, $depth_count[1], 'Two elements in taxonomy tree depth 1.');
+    $this->assertEqual(2, $depth_count[2], 'Two elements in taxonomy tree depth 2.');
+    $this->assertEqual(1, $depth_count[3], 'One element in taxonomy tree depth 3.');
+   }
 }
 
 /**
diff --git a/core/modules/translation/translation.module b/core/modules/translation/translation.module
index 5fbdf01b0c6..e121f041320 100644
--- a/core/modules/translation/translation.module
+++ b/core/modules/translation/translation.module
@@ -125,20 +125,25 @@ function translation_form_node_type_form_alter(&$form, &$form_state) {
 function translation_form_node_form_alter(&$form, &$form_state) {
   if (translation_supported_type($form['#node']->type)) {
     $node = $form['#node'];
-    $languages = language_list('enabled');
-    $disabled_languages = isset($languages[0]) ? $languages[0] : FALSE;
-    $translator_widget = $disabled_languages && user_access('translate content');
+
+    // Build two lists with the disabled and enabled languages.
+    $languages = language_list();
+    $grouped_languages = array();
+    foreach ($languages as $langcode => $language) {
+      $grouped_languages[(int) $language->enabled][$langcode] = $language;
+    }
+
+    $translator_widget = !empty($grouped_languages[0]) && user_access('translate content');
     $groups = array(t('Disabled'), t('Enabled'));
     // Allow translators to enter content in disabled languages. Translators
     // might need to distinguish between enabled and disabled languages, hence
     // we divide them in two option groups.
     if ($translator_widget) {
       $options = array($groups[1] => array(LANGUAGE_NONE => t('Language neutral')));
-      $language_list = locale_language_list('name', TRUE);
       foreach (array(1, 0) as $status) {
         $group = $groups[$status];
-        foreach ($languages[$status] as $langcode => $language) {
-          $options[$group][$langcode] = $language_list[$langcode];
+        foreach ($grouped_languages[$status] as $langcode => $language) {
+          $options[$group][$langcode] = $language->name;
         }
       }
       $form['language']['#options'] = $options;
@@ -208,8 +213,7 @@ function translation_node_view($node, $view_mode) {
   // If the site has no translations or is not multilingual we have no content
   // translation links to display.
   if (isset($node->tnid) && language_multilingual() && $translations = translation_node_get_translations($node->tnid)) {
-    $languages = language_list('enabled');
-    $languages = $languages[1];
+    $languages = language_list(TRUE);
 
     // There might be a language provider enabled defining custom language
     // switch links which need to be taken into account while generating the