Fn键（或称功能键、Function键）是电脑键盘中使用的一个组合性功能键，在苹果标准键盘和一些笔记本电脑中有使用。

Fn键可以在Windows系统笔记本电脑中用于调节相应硬件设置，如屏幕亮度、声音大小等。在Mac系苹果产品中，双击可启用听写。

在OS X系统下的快捷键

• Fn+↑或↓：向上／下滚动一页
• Fn+←或→：滚动到文稿开头／末尾
• Fn+delete：向前删除（也可以使用 control+D）

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Fn, short for function, is a modifier key on many keyboards, especially on laptops, used in a compact layout to combine keys which are usually kept separate. It is typically found on laptops due to their keyboard size restrictions. It is also found on many full-sized "multimedia" keyboards as the F-Lock key. It is mainly for the purpose of changing display or audio settings quickly, such as brightness, contrast, or volume, and is held down in conjunction with the appropriate key to change the settings.