diff --git wp-includes/functions.php wp-includes/functions.php
index c245af9..31612d3 100644
--- wp-includes/functions.php
+++ wp-includes/functions.php
@@ -3287,7 +3287,8 @@ function wp_is_numeric_array( $data ) {
  *                              against each object. Default empty array.
  * @param string      $operator Optional. The logical operation to perform. 'or' means
  *                              only one element from the array needs to match; 'and'
- *                              means all elements must match. Default 'and'.
+ *                              means all elements must match. 'not' means no elements may
+ *                              match. Default 'and'.
  * @param bool|string $field    A field from the object to place instead of the entire object.
  *                              Default false.
  * @return array A list of objects or object fields.
diff --git wp-includes/post.php wp-includes/post.php
index 59506f8..03cdad0 100644
--- wp-includes/post.php
+++ wp-includes/post.php
@@ -864,7 +864,7 @@ function get_post_type_object( $post_type ) {
  *                               or 'objects'. Default 'names'.
  * @param string       $operator Optional. The logical operation to perform. 'or' means only one
  *                               element from the array needs to match; 'and' means all elements
- *                               must match. Accepts 'or' or 'and'. Default 'and'.
+ *                               must match. 'not' means no elements may match. Default 'and'.
  * @return array A list of post type names or objects.
  */
 function get_post_types( $args = array(), $output = 'names', $operator = 'and' ) {