diff --git a/core/modules/system/core.api.php b/core/modules/system/core.api.php
index 17e9b28..131f99f 100644
--- a/core/modules/system/core.api.php
+++ b/core/modules/system/core.api.php
@@ -236,21 +236,27 @@
  *   to uninstall/reinstall or use a hook_update_N() function.
  * - Exporting and importing configuration.
  *
- * The file storage format for configuration information in Drupal is @link
- * http://en.wikipedia.org/wiki/YAML YAML files. @endlink Configuration is
+ * The file storage format for configuration information in Drupal is
+ * @link http://en.wikipedia.org/wiki/YAML YAML files. @endlink Configuration is
  * divided into files, each containing one configuration object. The file name
  * for a configuration object is equal to the unique name of the configuration,
  * with a '.yml' extension. The default configuration files for each module are
  * placed in the config/install directory under the top-level module directory,
  * so look there in most Core modules for examples.
  *
+ * @section sec_schema Configuration schema and translation
  * Each configuration file has a specific structure, which is expressed as a
  * YAML-based configuration schema. The configuration schema details the
  * structure of the configuration, its data types, and which of its values need
  * to be translatable. Each module needs to define its configuration schema in
  * files in the config/schema directory under the top-level module directory, so
- * look there in most Core modules for examples. Note that data types label,
- * text, and data_format are translatable; string is non-translatable text.
+ * look there in most Core modules for examples.
+ *
+ * Configuration can be internationalized; see the
+ * @link i18n Internationalization topic @endlink for more information. Data
+ * types label, text, and date_format in configuration schema are translatable;
+ * string is non-translatable text (the 'translatable' property on a schema
+ * data type definition indicates that it is translatable).
  *
  * @section sec_simple Simple configuration
  * The simple configuration API should be used for information that will always
diff --git a/core/modules/system/language.api.php b/core/modules/system/language.api.php
index d0ab879..107512a 100644
--- a/core/modules/system/language.api.php
+++ b/core/modules/system/language.api.php
@@ -77,12 +77,76 @@
  * providing a UI for translating UI text, it also imports community
  * translations from the
  * @link https://localize.drupal.org Drupal translation server. @endlink If
- * UI text in Drupal Core and contributed modules, themes, and installation
- * profiles is properly internationalized (as described above), the text is
- * automatically added to the translation server for community members to
- * translate.
+ * UI text and provided configuration in Drupal Core and contributed modules,
+ * themes, and installation profiles is properly internationalized (as described
+ * above), the text is automatically added to the translation server for
+ * community members to translate, via *.po files that are generated by
+ * scanning the project files.
+ *
+ * @section context Translation string sharing and context
+ * By default, translated strings are only translated once, no matter where
+ * they are being used. For instance, there are many forms with Save
+ * buttons on them, and they all would have t('Save') in their code. The
+ * translation system will only store this string once in the translation
+ * database, so that if the translation is updated, all forms using that text
+ * will get the updated translation.
+ *
+ * Because the source of translation strings is English, and some words in
+ * English have multiple meanings or uses, this centralized, shared translation
+ * string storage can sometimes lead to ambiguous translations that are not
+ * correct for every place the string is used. As an example, the English word
+ * "May", in a string by itself, could be part of a list of full month names or
+ * part of a list of 3-letter abbreviated month names. So, in languages where
+ * the month name for May is longer than 3 letters, you'd need to translate May
+ * differently depending on how it's being used. To address this problem, the
+ * translation system includes the concept of the "context" of a translated
+ * string, which can be used to disambiguate text for translators, and obtain
+ * the correct translation for each usage of the string.
+ *
+ * Here are some examples of how to provide translation context with strings, so
+ * that this information can be included in *.po files, displayed on the
+ * localization server for translators, and used to obtain the correct
+ * translation in the user interface:
+ * @code
+ * // PHP code
+ * t('May', array(), array('context' => 'Long month name');
+ * format_plural($count, '1 something', '@count somethings',
+ *   array(), array('context' => 'My context'));
+ *
+ * // JavaScript code
+ * Drupal.t('May', {}, {'context': 'Long month name'});
+ * Drupal.formatPlural(count, '1 something', '@count somethings', {},
+ *   {'context': 'My context'});
+ *
+ * // *.links.yml file
+ * title: 'May'
+ * title_context: 'Long month name'
+ *
+ * // *.routing.yml file
+ * my.route.name:
+ *   pattern: '/something'
+ *   defaults:
+ *     _title: 'May'
+ *     _title_context: 'Long month name'
+ *
+ * // Config schema to say that a certain piece of configuration should be
+ * // translatable using the Config Translation API. Note that the schema label
+ * // is also translatable, but it cannot have context.
+ * date_format:
+ *  type: string
+ *  label: 'PHP date format'
+ *  translatable: true
+ *  translation context: 'PHP date format'
+ *
+ * // Twig template
+ * {% trans with {'context': 'Long month name'} %}
+ *  May
+ * {% endtrans %}
+ *
  *
  * @see transliteration
+ * @see t()
+ * @see format_plural()
  * @}
  */