diff --git a/wp-includes/meta.php b/wp-includes/meta.php
index dfc0695..a423f52 100644
--- a/wp-includes/meta.php
+++ b/wp-includes/meta.php
@@ -1102,7 +1102,7 @@ function register_meta( $object_type, $meta_key, $args, $deprecated = null ) {
 		return true;
 	}
 
-	return new WP_Error( 'register_meta_failed', __( 'Sanitize and auth callbacks registered; meta key not registered.' ) );
+	return new WP_Error( 'register_meta_failed', __( 'Sanitize and auth callbacks are already registered, but meta key not yet registered.' ) );
 }
 
 /**
@@ -1126,7 +1126,7 @@ function registered_meta_key_exists( $object_type, $object_subtype, $meta_key )
 
 	// Only specific core object types are supported.
 	if ( ! wp_object_type_exists( $object_type ) ) {
-		return new WP_Error( 'invalid_meta_key', __( 'Invalid meta key. Not a core object type.' ) );
+		return new WP_Error( 'invalid_meta_key', __( 'Invalid meta key, it is not a core object type.' ) );
 	}
 
 	if ( ! isset( $wp_meta_keys[ $object_type ] ) ) {
@@ -1221,16 +1221,16 @@ function get_registered_metadata( $object_type, $object_subtype, $object_id, $me
 	global $wp_meta_keys;
 
 	if ( ! is_array( $wp_meta_keys ) ) {
-		return new WP_Error( 'invalid_meta_key', __( 'Invalid meta key. Not registered.' ) );
+		return new WP_Error( 'invalid_meta_key', __( 'Invalid meta key, it is not yet registered.' ) );
 	}
 
 	if ( ! wp_object_type_exists( $object_type ) ) {
-		return new WP_Error( 'invalid_meta_key', __( 'Invalid meta key. Not a core object type.' ) );
+		return new WP_Error( 'invalid_meta_key', __( 'Invalid meta key, it is not a core object type.' ) );
 	}
 
 	if ( ! empty( $meta_key ) ) {
 		if ( ! registered_meta_key_exists( $object_type, $object_subtype, $meta_key ) ) {
-			return new WP_Error( 'invalid_meta_key', __( 'Invalid meta key. Not registered.' ) );
+			return new WP_Error( 'invalid_meta_key', __( 'Invalid meta key, it is not yet registered.' ) );
 		}
 		$meta_keys = get_registered_meta_keys( $object_type, $object_subtype );
 		$meta_key_data = $meta_keys[ $meta_key ];