docs($rootScope.Scope): grammar

Closes #15263

src/ng/rootScope.js

@@ -436,8 +436,8 @@ function $RootScopeProvider() {
        * A variant of {@link ng.$rootScope.Scope#$watch $watch()} where it watches an array of `watchExpressions`.
        * If any one expression in the collection changes the `listener` is executed.
        *
-       * - The items in the `watchExpressions` array are observed via standard $watch operation and are examined on every
-       *   call to $digest() to see if any items changes.
+       * - The items in the `watchExpressions` array are observed via the standard `$watch` operation. Their return
+       *   values are examined for changes on every call to `$digest`.
        * - The `listener` is called whenever any expression in the `watchExpressions` array changes.
        *
        * @param {Array.<string|Function(scope)>} watchExpressions Array of expressions that will be individually