diff -u b/core/lib/Drupal/Core/Config/ConfigFactoryInterface.php b/core/lib/Drupal/Core/Config/ConfigFactoryInterface.php
--- b/core/lib/Drupal/Core/Config/ConfigFactoryInterface.php
+++ b/core/lib/Drupal/Core/Config/ConfigFactoryInterface.php
@@ -34,7 +34,7 @@
    * Gets the override state.
    *
    * @return bool
-   *   Whether the configuration is overridden.
+   *   Get the override state.
    */
   public function getOverrideState();
 
@@ -58,7 +58,7 @@
    * @param array $names
    *   List of names of configuration objects.
    *
-   * @return \Drupal\Core\Config\Config[]
+   * @return array
    *   List of successfully loaded configuration objects, keyed by name.
    */
   public function loadMultiple(array $names);
@@ -66,7 +66,7 @@
   /**
    * Resets and re-initializes configuration objects. Internal use only.
    *
-   * @param string|null $name
+   * @param string $name
    *   (optional) The name of the configuration object to reset. If omitted, all
    *   configuration objects are reset.
    *
@@ -119,7 +119,7 @@
   /**
    * Sets the language to be used in configuration overrides.
    *
-   * @param \Drupal\Core\Language\Language|null $language
+   * @param \Drupal\Core\Language\Language $language
    *   The language object to be set on the config factory. Used to override
    *   configuration by language.
    *
@@ -140,10 +140,9 @@
   public function setLanguageFromDefault(LanguageDefault $language_default);
 
   /**
-   * Gets the language used to override configuration.
+   * Gets the language Used to override configuration.
    *
    * @return \Drupal\Core\Language\Language
-   *   The language used to override configuration.
    */
   public function getLanguage();
 
@@ -174,7 +173,7 @@
    *
    * @return bool|string
    *   The configuration name for configuration object providing overrides.
-   *   Returns FALSE if the name already starts with the language config prefix.
+   *   Returns false if the name already starts with the language config prefix.
    */
   public function getLanguageConfigName($langcode, $name);