diff --git a/core/modules/node/node.api.php b/core/modules/node/node.api.php
index f1a1a37..45a02bf 100644
--- a/core/modules/node/node.api.php
+++ b/core/modules/node/node.api.php
@@ -350,24 +350,6 @@ function hook_node_access(\Drupal\node\NodeInterface $node, $op, $account, $lang
 }
 
 /**
- * Act on a node object about to be shown on the add/edit form.
- *
- * This hook is invoked from NodeForm::prepareEntity().
- *
- * @param \Drupal\node\NodeInterface $node
- *   The node that is about to be shown on the form.
- * @param $operation
- *   The current operation.
- * @param array $form_state
- *   An associative array containing the current state of the form.
- */
-function hook_node_prepare_form(\Drupal\node\NodeInterface $node, $operation, array &$form_state) {
-  if (!isset($node->my_rating)) {
-    $node->my_rating = \Drupal::config("my_rating_{$node->bundle()}")->get('enabled');
-  }
-}
-
-/**
  * Act on a node being displayed as a search result.
  *
  * This hook is invoked from the node search plugin during search execution,
@@ -440,6 +422,8 @@ function hook_node_update_index(\Drupal\node\NodeInterface $node, $langcode) {
  *   The form being used to edit the node.
  * @param $form_state
  *   The form state array.
+ *
+ * @ingroup entity_crud
  */
 function hook_node_validate(\Drupal\node\NodeInterface $node, $form, &$form_state) {
   if (isset($node->end) && isset($node->start)) {
@@ -465,6 +449,8 @@ function hook_node_validate(\Drupal\node\NodeInterface $node, $form, &$form_stat
  *   The form being used to edit the node.
  * @param $form_state
  *   The form state array.
+ *
+ * @ingroup entity_crud
  */
 function hook_node_submit(\Drupal\node\NodeInterface $node, $form, &$form_state) {
   // Decompose the selected menu parent option into 'menu_name' and 'plid', if
diff --git a/core/modules/system/core.api.php b/core/modules/system/core.api.php
index 4eb5fe0..16f1434 100644
--- a/core/modules/system/core.api.php
+++ b/core/modules/system/core.api.php
@@ -287,7 +287,8 @@
  *     entities), to provide an administrative overview for your entities.
  *   - add and edit forms, or default form: Define a class (or two) that
  *     extend(s) \Drupal\Core\Entity\EntityForm to provide add and edit forms
- *     for your entities.
+ *     for your entities. For content entities, base class
+ *     \Drupal\Core\Entity\ContentEntityForm is a better starting point.
  *   - delete form: Define a class that extends
  *     \Drupal\Core\Entity\EntityConfirmFormBase to provide a delete
  *     confirmation form for your entities.
@@ -426,7 +427,7 @@
  * @code
  * // If the entity supports translation, load the translation.
  * $entity = $entity->getTranslation($language->id);
- * $build = $renderer->view($entity, 'view_mode_name', $language->id);
+ * $build = $viewer->view($entity, 'view_mode_name', $language->id);
  * // $build is a render array.
  * $rendered = drupal_render($build);
  * @endcode
diff --git a/core/modules/system/entity.api.php b/core/modules/system/entity.api.php
index b7a1913..c3e6669 100644
--- a/core/modules/system/entity.api.php
+++ b/core/modules/system/entity.api.php
@@ -11,9 +11,9 @@
 use Drupal\Core\Render\Element;
 
 /**
- * @defgroup entity_crud Entity CRUD and view hooks
+ * @defgroup entity_crud Entity CRUD, editing, and view hooks
  * @{
- * Hooks used in entity view, create, read, update, and delete operations.
+ * Hooks used in various entity operations.
  *
  * Entity create, read, update, and delete (CRUD) operations are performed by
  * entity storage controllers; see the
@@ -31,6 +31,11 @@
  * information. Most view builders extend or use the default class
  * \Drupal\Core\Entity\EntityViewBuilder.
  *
+ * Entity editing (including adding new entities) is handled by entity form
+ * controllers; see the @link entity_api Entity API topic @endlink for more
+ * information. Most entity editing forms extend base classes
+ * \Drupal\Core\Entity\EntityForm or \Drupal\Core\Entity\ContentEntityForm.
+ *
  * This topic lists all of the entity CRUD and view operations, and the hooks
  * and other operations that are invoked (in order) for each operation. Some
  * notes:
@@ -116,6 +121,17 @@
  * - Comment: hook_comment_publish() and hook_comment_unpublish() as
  *   appropriate.
  *
+ * @section edit Editing operations
+ * When an entity's add/edit form is used to add or edit an entity, there
+ * are several hooks that are invoked:
+ * - hook_entity_prepare_form()
+ * - hook_ENTITY_TYPE_prepare_form()
+ * - hook_entity_form_display_alter()
+ *
+ * Some specific entity types have additional hooks that are run during
+ * various steps in the process:
+ * - Node entities: hook_node_validate() and hook_submit().
+ *
  * @section delete Delete operations
  * To delete one or more entities, load them and then delete them:
  * @code
@@ -155,7 +171,7 @@
  * @code
  * // If the entity supports translation, load the translation.
  * $entity = $entity->getTranslation($language->id);
- * $build = $renderer->view($entity, 'view_mode_name', $language->id);
+ * $build = $viewer->view($entity, 'view_mode_name', $language->id);
  * @endcode
  * You can also use the viewMultiple() method to view multiple entities.
  *
@@ -172,6 +188,7 @@
  *
  * During the rendering operation, the default entity viewer runs the following
  * hooks and operations in the pre-render step:
+ * - hook_entity_view_display_alter()
  * - hook_entity_prepare_view()
  * - Entity fields are loaded, and render arrays are built for them using
  *   their formatters.
@@ -1136,6 +1153,8 @@ function hook_entity_build_defaults_alter(array &$build, \Drupal\Core\Entity\Ent
  *   - entity_type: The entity type, e.g., 'node' or 'user'.
  *   - bundle: The bundle, e.g., 'page' or 'article'.
  *   - view_mode: The view mode, e.g. 'full', 'teaser'...
+ *
+ * @ingroup entity_crud
  */
 function hook_entity_view_display_alter(\Drupal\Core\Entity\Display\EntityViewDisplayInterface $display, array $context) {
   // Leave field labels out of the search index.
@@ -1195,6 +1214,9 @@ function hook_entity_display_build_alter(&$build, $context) {
  *   An associative array containing the current state of the form.
  *
  * @see \Drupal\Core\Entity\EntityForm::prepareEntity()
+ * @see hook_ENTITY_TYPE_prepare_form()
+ *
+ * @ingroup entity_crud
  */
 function hook_entity_prepare_form(\Drupal\Core\Entity\EntityInterface $entity, $operation, array &$form_state) {
   if ($operation == 'edit') {
@@ -1204,6 +1226,32 @@ function hook_entity_prepare_form(\Drupal\Core\Entity\EntityInterface $entity, $
 }
 
 /**
+ * Acts on a particular type of entity object about to be in an entity form.
+ *
+ * This can be typically used to pre-fill entity values or change the form state
+ * before the entity form is built. It is invoked just once when first building
+ * the entity form. Rebuilds will not trigger a new invocation.
+ *
+ * @param \Drupal\Core\Entity\EntityInterface $entity
+ *   The entity that is about to be shown on the form.
+ * @param $operation
+ *   The current operation.
+ * @param array $form_state
+ *   An associative array containing the current state of the form.
+ *
+ * @see \Drupal\Core\Entity\EntityForm::prepareEntity()
+ * @see hook_entity_prepare_form()
+ *
+ * @ingroup entity_crud
+ */
+function hook_ENTITY_TYPE_prepare_form(\Drupal\Core\Entity\EntityInterface $entity, $operation, array &$form_state) {
+  if ($operation == 'edit') {
+    $entity->label->value = 'Altered label';
+    $form_state['mymodule']['label_altered'] = TRUE;
+  }
+}
+
+/**
  * Alter the settings used for displaying an entity form.
  *
  * @param \Drupal\Core\Entity\Display\EntityFormDisplayInterface $form_display
@@ -1214,6 +1262,8 @@ function hook_entity_prepare_form(\Drupal\Core\Entity\EntityInterface $entity, $
  *   - entity_type: The entity type, e.g., 'node' or 'user'.
  *   - bundle: The bundle, e.g., 'page' or 'article'.
  *   - form_mode: The form mode, e.g. 'default', 'profile', 'register'...
+ *
+ * @ingroup entity_crud
  */
 function hook_entity_form_display_alter(\Drupal\Core\Entity\Display\EntityFormDisplayInterface $form_display, array $context) {
   // Hide the 'user_picture' field from the register form.