diff --git a/core/lib/Drupal/Core/Extension/ExtensionList.php b/core/lib/Drupal/Core/Extension/ExtensionList.php
index 6d7ae6c1ea..4b7371c869 100644
--- a/core/lib/Drupal/Core/Extension/ExtensionList.php
+++ b/core/lib/Drupal/Core/Extension/ExtensionList.php
@@ -210,8 +210,8 @@ protected function getPathnamesCacheId() {
    *   TRUE if the extension exists (regardless installed or not) and FALSE if
    *   not.
    */
-  public function extensionExists($extension_name) {
-    $extensions = $this->listExtensions();
+  public function exists($extension_name) {
+    $extensions = $this->list();
     return isset($extensions[$extension_name]);
   }
 
@@ -228,7 +228,7 @@ public function extensionExists($extension_name) {
    *   If there is no extension with the supplied extension human name.
    */
   public function getName($extension_name) {
-    return $this->getExtension($extension_name)->info['name'];
+    return $this->get($extension_name)->info['name'];
   }
 
   /**
@@ -243,8 +243,8 @@ public function getName($extension_name) {
    * @throws \InvalidArgumentException
    *   If there is no extension with the supplied name.
    */
-  public function getExtension($extension_name) {
-    $extensions = $this->listExtensions();
+  public function get($extension_name) {
+    $extensions = $this->list();
     if (isset($extensions[$extension_name])) {
       return $extensions[$extension_name];
     }
@@ -258,7 +258,7 @@ public function getExtension($extension_name) {
    * @return \Drupal\Core\Extension\Extension[]
    *   Processed extension objects, keyed by extension machine name.
    */
-  public function listExtensions() {
+  public function list() {
     if ($this->extensions !== NULL) {
       return $this->extensions;
     }
@@ -266,7 +266,7 @@ public function listExtensions() {
       $this->extensions = $cache->data;
       return $this->extensions;
     }
-    $extensions = $this->doListExtensions();
+    $extensions = $this->doList();
     $this->cache->set($this->getListCacheId(), $extensions);
     $this->extensions = $extensions;
     return $this->extensions;
@@ -294,7 +294,7 @@ protected function doScanExtensions() {
    * @throws \Drupal\Core\Extension\InfoParserException
    *   If one of the .info.yml files is incomplete, or causes a parsing error.
    */
-  protected function doListExtensions() {
+  protected function doList() {
     // Find extensions.
     $extensions = $this->doScanExtensions();
 
@@ -398,7 +398,7 @@ public function getAllInstalledInfo() {
   protected function recalculateInfo() {
     return array_map(function (Extension $extension) {
       return $extension->info;
-    }, $this->listExtensions());
+    }, $this->list());
   }
 
   /**
@@ -432,7 +432,7 @@ public function getPathnames() {
    *   An array of .info.yml file locations keyed by the extension machine name.
    */
   protected function recalculatePathnames() {
-    $extensions = $this->listExtensions();
+    $extensions = $this->list();
     ksort($extensions);
 
     return array_map(function (Extension $extension) {
@@ -519,6 +519,9 @@ public function getPathname($extension_name) {
 
   /**
    * Gets the path to an extension of a specific type (module, theme, etc.).
+   * 
+   * The path is the directory in which the .info file is located. This name is
+   * coming from \SplFileInfo.
    *
    * @param string $extension_name
    *   The name of the extension for which the path is requested.
diff --git a/core/lib/Drupal/Core/Extension/ModuleExtensionList.php b/core/lib/Drupal/Core/Extension/ModuleExtensionList.php
index 00f154bc91..57198fea5f 100644
--- a/core/lib/Drupal/Core/Extension/ModuleExtensionList.php
+++ b/core/lib/Drupal/Core/Extension/ModuleExtensionList.php
@@ -127,7 +127,7 @@ protected function getProfileDirectories(ExtensionDiscovery $discovery) {
    *   The active profile, if there is one.
    */
   protected function getActiveProfile() {
-    $profiles = $this->profileList->listExtensions();
+    $profiles = $this->profileList->list();
     if ($this->installProfile && isset($profiles[$this->installProfile])) {
       return $profiles[$this->installProfile];
     }
@@ -155,9 +155,9 @@ protected function doScanExtensions() {
   /**
    * {@inheritdoc}
    */
-  protected function doListExtensions() {
+  protected function doList() {
     // Find modules.
-    $extensions = parent::doListExtensions();
+    $extensions = parent::doList();
     // It is possible that a module was marked as required by
     // hook_system_info_alter() and modules that it depends on are not required.
     foreach ($extensions as $extension) {
diff --git a/core/lib/Drupal/Core/Updater/Module.php b/core/lib/Drupal/Core/Updater/Module.php
index 0eaf46c634..35232b3c0d 100644
--- a/core/lib/Drupal/Core/Updater/Module.php
+++ b/core/lib/Drupal/Core/Updater/Module.php
@@ -49,7 +49,9 @@ public static function getRootDirectoryRelativePath() {
   public function isInstalled() {
     // Check if the module exists in the file system, regardless of whether it
     // is enabled or not.
-    return \Drupal::service('extension.list.module')->extensionExists($this->name);
+    /** @var \Drupal\Core\Extension\ExtensionList $module_extension_list */
+    $module_extension_list = \Drupal::service('extension.list.module');
+    return $module_extension_list->exists($this->name);
   }
 
   /**
diff --git a/core/modules/book/tests/src/Kernel/BookUninstallTest.php b/core/modules/book/tests/src/Kernel/BookUninstallTest.php
index 279873481b..817b1335c1 100644
--- a/core/modules/book/tests/src/Kernel/BookUninstallTest.php
+++ b/core/modules/book/tests/src/Kernel/BookUninstallTest.php
@@ -76,7 +76,7 @@ public function testBookUninstall() {
 
     $book_node->delete();
     // No nodes exist therefore the book module is not required.
-    $module_data = \Drupal::service('extension.list.module')->reset()->listExtensions();
+    $module_data = \Drupal::service('extension.list.module')->reset()->list();
     $this->assertFalse(isset($module_data['book']->info['required']), 'The book module is not required.');
 
     $node = Node::create(['title' => $this->randomString(), 'type' => $content_type->id()]);
diff --git a/core/modules/filter/tests/src/Kernel/FilterAPITest.php b/core/modules/filter/tests/src/Kernel/FilterAPITest.php
index 6b3eee0db0..ed2db2f343 100644
--- a/core/modules/filter/tests/src/Kernel/FilterAPITest.php
+++ b/core/modules/filter/tests/src/Kernel/FilterAPITest.php
@@ -485,7 +485,7 @@ public function testDependencyRemoval() {
 
     drupal_static_reset('filter_formats');
     \Drupal::entityManager()->getStorage('filter_format')->resetCache();
-    $module_data = \Drupal::service('extension.list.module')->reset()->listExtensions();
+    $module_data = \Drupal::service('extension.list.module')->reset()->list();
     $this->assertFalse(isset($module_data['filter_test']->info['required']), 'The filter_test module is required.');
 
     // Verify that a dependency exists on the module that provides the filter
diff --git a/core/modules/system/system.module b/core/modules/system/system.module
index 075cc803e8..115635198f 100644
--- a/core/modules/system/system.module
+++ b/core/modules/system/system.module
@@ -1006,12 +1006,12 @@ function _system_rebuild_module_data_ensure_required($module, &$modules) {
  *   An associative array of module information.
  *
  * @deprecated in Drupal 8.4.x and will be removed before Drupal 9.0.0.
- *   Use \Drupal::service('extension.list.module')->reset()->listExtensions()
+ *   Use \Drupal::service('extension.list.module')->reset()->list()
  *   instead. Note: You probably don't need the reset() method.
  */
 function _system_rebuild_module_data() {
-  @trigger_error("_system_rebuild_module_data() is deprecated in Drupal 8.4.0 and will be removed before Drupal 9.0.0. Instead, you should use \\Drupal::service('extension.list.module')->reset()->listExtensions(). See https://www.drupal.org/node/2709919", E_USER_DEPRECATED);
-  return \Drupal::service('extension.list.module')->reset()->listExtensions();
+  @trigger_error("_system_rebuild_module_data() is deprecated in Drupal 8.4.0 and will be removed before Drupal 9.0.0. Instead, you should use \\Drupal::service('extension.list.module')->reset()->list(). See https://www.drupal.org/node/2709919", E_USER_DEPRECATED);
+  return \Drupal::service('extension.list.module')->reset()->list();
 }
 
 /**
@@ -1023,8 +1023,8 @@ function _system_rebuild_module_data() {
  * @deprecated in Drupal 8.4.x and will be removed before Drupal 9.0.0.
  */
 function system_rebuild_module_data() {
-  @trigger_error("system_rebuild_module_data() is deprecated in Drupal 8.4.0 and will be removed before Drupal 9.0.0. Instead, you should use \\Drupal::service('extension.list.module')->reset()->listExtensions(). See https://www.drupal.org/node/2709919", E_USER_DEPRECATED);
-  return \Drupal::service('extension.list.module')->reset()->listExtensions();
+  @trigger_error("system_rebuild_module_data() is deprecated in Drupal 8.4.0 and will be removed before Drupal 9.0.0. Instead, you should use \\Drupal::service('extension.list.module')->reset()->list(). See https://www.drupal.org/node/2709919", E_USER_DEPRECATED);
+  return \Drupal::service('extension.list.module')->reset()->list();
 }
 
 /**
diff --git a/core/modules/system/tests/src/Kernel/Extension/ModuleHandlerTest.php b/core/modules/system/tests/src/Kernel/Extension/ModuleHandlerTest.php
index 59382d72a5..dcad79ee13 100644
--- a/core/modules/system/tests/src/Kernel/Extension/ModuleHandlerTest.php
+++ b/core/modules/system/tests/src/Kernel/Extension/ModuleHandlerTest.php
@@ -182,7 +182,7 @@ public function testUninstallProfileDependency() {
     drupal_get_filename('profile', $profile, 'core/profiles/' . $profile . '/' . $profile . '.info.yml');
     $this->enableModules(['module_test', $profile]);
 
-    $data = \Drupal::service('extension.list.module')->reset()->listExtensions();
+    $data = \Drupal::service('extension.list.module')->reset()->list();
     $this->assertTrue(isset($data[$profile]->requires[$dependency]));
 
     $this->moduleInstaller()->install([$dependency]);
diff --git a/core/tests/Drupal/KernelTests/Core/Extension/ModuleExtensionListTest.php b/core/tests/Drupal/KernelTests/Core/Extension/ModuleExtensionListTest.php
index 70512c644e..c40fcee98a 100644
--- a/core/tests/Drupal/KernelTests/Core/Extension/ModuleExtensionListTest.php
+++ b/core/tests/Drupal/KernelTests/Core/Extension/ModuleExtensionListTest.php
@@ -12,9 +12,9 @@
 class ModuleExtensionListTest extends KernelTestBase {
 
   /**
-   * @covers ::listExtensions
+   * @covers ::list
    */
-  public function testListExtensions() {
+  public function testlist() {
     $settings = Settings::getAll();
     $settings['install_profile'] = 'testing';
     new Settings($settings);
@@ -29,7 +29,7 @@ public function testListExtensions() {
 
     /** @var \Drupal\Core\Extension\ModuleExtensionList $module_extension_list */
     $module_extension_list = \Drupal::service('extension.list.module');
-    $extensions = $module_extension_list->listExtensions();
+    $extensions = $module_extension_list->list();
 
     $this->assertArrayHasKey('testing', $extensions);
     $this->assertEquals(1000, $extensions['testing']->weight);
diff --git a/core/tests/Drupal/Tests/Core/Extension/ExtensionListTest.php b/core/tests/Drupal/Tests/Core/Extension/ExtensionListTest.php
index da4b322a14..c50be34488 100644
--- a/core/tests/Drupal/Tests/Core/Extension/ExtensionListTest.php
+++ b/core/tests/Drupal/Tests/Core/Extension/ExtensionListTest.php
@@ -56,7 +56,7 @@ public function testGetExtensionWithNonExistingExtension() {
     $test_extension_list->setExtensionDiscovery($extension_discovery->reveal());
 
     $this->setExpectedException(\InvalidArgumentException::class);
-    $test_extension_list->getExtension('test_name');
+    $test_extension_list->get('test_name');
   }
 
   /**
@@ -65,18 +65,18 @@ public function testGetExtensionWithNonExistingExtension() {
   public function testGetExtension() {
     $test_extension_list = $this->setupTestExtensionList();
 
-    $extension = $test_extension_list->getExtension('test_name');
+    $extension = $test_extension_list->get('test_name');
     $this->assertInstanceOf(Extension::class, $extension);
     $this->assertEquals('test_name', $extension->getName());
   }
 
   /**
-   * @covers ::listExtensions
+   * @covers ::list
    */
-  public function testListExtensions() {
+  public function testList() {
     $test_extension_list = $this->setupTestExtensionList();
 
-    $extensions = $test_extension_list->listExtensions();
+    $extensions = $test_extension_list->list();
     $this->assertCount(1, $extensions);
     $this->assertEquals('test_name', $extensions['test_name']->getName());
   }