diff -u b/core/modules/field/lib/Drupal/field/FieldInfo.php b/core/modules/field/lib/Drupal/field/FieldInfo.php
--- b/core/modules/field/lib/Drupal/field/FieldInfo.php
+++ b/core/modules/field/lib/Drupal/field/FieldInfo.php
@@ -71,7 +71,7 @@
   /**
    * List of $field structures keyed by ID. Includes deleted fields.
    *
-   * @var array
+   * @var \Drupal\field\FieldInterface[]
    */
   protected $fieldsById = array();
 
@@ -219,7 +219,7 @@
    * Returns all active fields, including deleted ones.
    *
    * @return \Drupal\field\FieldInterface[]
-   *   An array of field definitions, keyed by field ID.
+   *   An array of field entities, keyed by field ID.
    */
   public function getFields() {
     // Read from the "static" cache.
@@ -340,7 +340,7 @@
   }
 
   /**
-   * Returns a field definition from a field ID.
+   * Returns a field entity from a field ID.
    *
    * This method only retrieves active fields, deleted or not.
    *
@@ -348,7 +348,7 @@
    *   The field ID.
    *
    * @return \Drupal\field\FieldInterface|null
-   *   The field definition, or NULL if no field was found.
+   *   The field entity, or NULL if no field was found.
    */
   public function getFieldById($field_id) {
     // Read from the "static" cache.
@@ -392,7 +392,7 @@
    *   The bundle name.
    *
    * @return \Drupal\field\FieldInstanceInterface[]
-   *   The array of instance definitions, keyed by field name.
+   *   An array of field instance entities, keyed by field name.
    */
   public function getBundleInstances($entity_type, $bundle) {
     // Read from the "static" cache.
@@ -496,7 +496,7 @@
   }
 
   /**
-   * Returns a field instance definition.
+   * Returns a field instance.
    *
    * @param string $entity_type
    *   The entity type for the instance.
@@ -506,7 +506,7 @@
    *   The field name for the instance.
    *
    * @return \Drupal\field\FieldInstanceInterface|null
-   *   The field instance definition, or NULL if it does not exist.
+   *   The field instance entity, or NULL if it does not exist.
    */
   function getInstance($entity_type, $bundle, $field_name) {
     $info = $this->getBundleInstances($entity_type, $bundle);
@@ -554,13 +554,13 @@
   }
 
   /**
-   * Prepares a field definition for the current run-time context.
+   * Prepares a field for the current run-time context.
    *
    * @param \Drupal\field\FieldInterface $field
-   *   The raw field structure as read from the database.
+   *   The field entity to update.
    *
    * @return \Drupal\field\FieldInterface
-   *   The field definition completed for the current runtime context.
+   *   The field that was prepared.
    */
   public function prepareField(FieldInterface $field) {
     // Make sure all expected field settings are present.
@@ -570,13 +570,13 @@
   }
 
   /**
-   * Prepares an instance definition for the current run-time context.
+   * Prepares a field instance for the current run-time context.
    *
    * @param \Drupal\field\FieldInstanceInterface $instance
-   *   The instance definition.
+   *   The field instance entity to prepare.
    *
    * @return \Drupal\field\FieldInstanceInterface
-   *   The field instance array completed for the current runtime context.
+   *   The field instance that was prepared.
    */
   public function prepareInstance(FieldInstanceInterface $instance) {
     // Make sure all expected instance settings are present.