Fn key - Computer Definition
(FuNction key) A keyboard modifier key that works like a Shift key to activate a second function on a dual-purpose key. Commonly found on laptop keyboards, the Fn key is used to control hardware functions such as screen brightness and speaker volume. It may also be found on extra small keyboards for desktop computers, typically for Page Up and Page Down, which are combined with Up Arrow and Down Arrow. See function key and computer keyboard.