diff --git a/wp-includes/comment.php b/wp-includes/comment.php
index de6b392a2c..8246fc9bc5 100644
--- a/wp-includes/comment.php
+++ b/wp-includes/comment.php
@@ -517,9 +517,11 @@ function get_comment_meta( $comment_id, $key = '', $single = false ) {
  * @param string $meta_key   Metadata key.
  * @param mixed  $meta_value Metadata value. Must be serializable if non-scalar.
  * @param mixed  $prev_value Optional. Previous value to check before updating.
- *                           Default empty.
+ *                           If specified, only update existing metadata entries with
+ *                           this value. Otherwise, update all entries. Default empty.
  * @return int|bool Meta ID if the key didn't exist, true on successful update,
- *                  false on failure.
+ *                  false on failure or if the value passed to the function
+ *                  is the same as the one that is already in the database.
  */
 function update_comment_meta( $comment_id, $meta_key, $meta_value, $prev_value = '' ) {
 	return update_metadata( 'comment', $comment_id, $meta_key, $meta_value, $prev_value );
diff --git a/wp-includes/meta.php b/wp-includes/meta.php
index cacb8be305..f434ef3b5c 100644
--- a/wp-includes/meta.php
+++ b/wp-includes/meta.php
@@ -148,10 +148,14 @@ function add_metadata( $meta_type, $object_id, $meta_key, $meta_value, $unique =
  * @param int    $object_id  ID of the object metadata is for.
  * @param string $meta_key   Metadata key.
  * @param mixed  $meta_value Metadata value. Must be serializable if non-scalar.
- * @param mixed  $prev_value Optional. If specified, only update existing metadata entries
- *                           with this value. Otherwise, update all entries. Default empty.
- * @return int|bool The new meta field ID if a field with the given key didn't exist and was
- *                  therefore added, true on successful update, false on failure.
+ * @param mixed  $prev_value Optional. Previous value to check before updating.
+ *                           If specified, only update existing metadata entries with
+ *                           this value. Otherwise, update all entries. Default empty.
+ * @return int|bool The new meta field ID if a field with the given key didn't exist
+ *                  and was therefore added, true on successful update,
+ *                  false on failure or if the value passed to the function
+ *                  is the same as the one that is already in the database.
+
  */
 function update_metadata( $meta_type, $object_id, $meta_key, $meta_value, $prev_value = '' ) {
 	global $wpdb;
@@ -195,8 +199,9 @@ function update_metadata( $meta_type, $object_id, $meta_key, $meta_value, $prev_
 	 * @param int       $object_id  ID of the object metadata is for.
 	 * @param string    $meta_key   Metadata key.
 	 * @param mixed     $meta_value Metadata value. Must be serializable if non-scalar.
-	 * @param mixed     $prev_value Optional. If specified, only update existing metadata entries
-	 *                              with this value. Otherwise, update all entries.
+	 * @param mixed     $prev_value Optional. Previous value to check before updating.
+	 *                              If specified, only update existing metadata entries with
+	 *                              this value. Otherwise, update all entries.
 	 */
 	$check = apply_filters( "update_{$meta_type}_metadata", null, $object_id, $meta_key, $meta_value, $prev_value );
 	if ( null !== $check ) {
diff --git a/wp-includes/ms-site.php b/wp-includes/ms-site.php
index 5124c4ad50..7070baefd9 100644
--- a/wp-includes/ms-site.php
+++ b/wp-includes/ms-site.php
@@ -1107,9 +1107,11 @@ function get_site_meta( $site_id, $key = '', $single = false ) {
  * @param string $meta_key   Metadata key.
  * @param mixed  $meta_value Metadata value. Must be serializable if non-scalar.
  * @param mixed  $prev_value Optional. Previous value to check before updating.
- *                           Default empty.
+ *                           If specified, only update existing metadata entries with
+ *                           this value. Otherwise, update all entries. Default empty.
  * @return int|bool Meta ID if the key didn't exist, true on successful update,
- *                  false on failure.
+ *                  false on failure or if the value passed to the function
+ *                  is the same as the one that is already in the database.
  */
 function update_site_meta( $site_id, $meta_key, $meta_value, $prev_value = '' ) {
 	return update_metadata( 'blog', $site_id, $meta_key, $meta_value, $prev_value );
diff --git a/wp-includes/post.php b/wp-includes/post.php
index 1ab5ab1501..c76381ce95 100644
--- a/wp-includes/post.php
+++ b/wp-includes/post.php
@@ -2140,9 +2140,11 @@ function get_post_meta( $post_id, $key = '', $single = false ) {
  * @param string $meta_key   Metadata key.
  * @param mixed  $meta_value Metadata value. Must be serializable if non-scalar.
  * @param mixed  $prev_value Optional. Previous value to check before updating.
- *                           Default empty.
+ *                           If specified, only update existing metadata entries with
+ *                           this value. Otherwise, update all entries. Default empty.
  * @return int|bool Meta ID if the key didn't exist, true on successful update,
- *                  false on failure.
+ *                  false on failure or if the value passed to the function
+ *                  is the same as the one that is already in the database.
  */
 function update_post_meta( $post_id, $meta_key, $meta_value, $prev_value = '' ) {
 	// Make sure meta is added to the post, not a revision.
diff --git a/wp-includes/taxonomy.php b/wp-includes/taxonomy.php
index d8df47e5fd..d02aa9b9e4 100644
--- a/wp-includes/taxonomy.php
+++ b/wp-includes/taxonomy.php
@@ -1274,10 +1274,12 @@ function get_term_meta( $term_id, $key = '', $single = false ) {
  * @param string $meta_key   Metadata key.
  * @param mixed  $meta_value Metadata value. Must be serializable if non-scalar.
  * @param mixed  $prev_value Optional. Previous value to check before updating.
- *                           Default empty.
+ *                           If specified, only update existing metadata entries with
+ *                           this value. Otherwise, update all entries. Default empty.
  * @return int|bool|WP_Error Meta ID if the key didn't exist. true on successful update,
- *                           false on failure. WP_Error when term_id is ambiguous
- *                           between taxonomies.
+ *                           false on failure or if the value passed to the function
+ *                           is the same as the one that is already in the database.
+ *                           WP_Error when term_id is ambiguous between taxonomies.
  */
 function update_term_meta( $term_id, $meta_key, $meta_value, $prev_value = '' ) {
 	if ( wp_term_is_shared( $term_id ) ) {
diff --git a/wp-includes/user.php b/wp-includes/user.php
index 6d75e07c1e..63047c7219 100644
--- a/wp-includes/user.php
+++ b/wp-includes/user.php
@@ -853,9 +853,11 @@ function get_user_meta( $user_id, $key = '', $single = false ) {
  * @param string $meta_key   Metadata key.
  * @param mixed  $meta_value Metadata value. Must be serializable if non-scalar.
  * @param mixed  $prev_value Optional. Previous value to check before updating.
- *                           Default empty.
+ *                           If specified, only update existing metadata entries with
+ *                           this value. Otherwise, update all entries. Default empty.
  * @return int|bool Meta ID if the key didn't exist, true on successful update,
- *                  false on failure.
+ *                  false on failure or if the value passed to the function
+ *                  is the same as the one that is already in the database.
  */
 function update_user_meta( $user_id, $meta_key, $meta_value, $prev_value = '' ) {
 	return update_metadata( 'user', $user_id, $meta_key, $meta_value, $prev_value );
diff --git a/wp-includes/version.php b/wp-includes/version.php
index b6a9f70ae8..ffc03631d1 100644
--- a/wp-includes/version.php
+++ b/wp-includes/version.php
@@ -13,7 +13,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '5.5-alpha-48213';
+$wp_version = '5.5-alpha-48214';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.