diff --git a/core/modules/field/field.api.php b/core/modules/field/field.api.php
index 774d8b5..2b67aca 100644
--- a/core/modules/field/field.api.php
+++ b/core/modules/field/field.api.php
@@ -542,8 +542,9 @@ function hook_field_storage_update_field($field, $prior_field, $has_data) {
 /**
  * Define custom delete behavior for this module's field types.
  *
- * This hook is invoked just before the data is deleted from field storage
- * in field_attach_delete().
+ * This hook is invoked on the module that defines a field and just before the
+ * data of particular field instance is deleted from field storage in
+ * field_attach_delete().
  *
  * @param $entity_type
  *   The type of $entity.