转换键，又名Alt键，是电脑键盘上起切换（Alternate）作用的按键，它通常与其他键组合发挥作用，单独是没有作用的。

与其他按键组合工作时，可以实现切换窗口、关闭活动的应用进程、选择菜单、命令和选项等功能。

For a list of keyboard shortcuts, see Table of keyboard shortcuts

⌥ Opt or Alt The Alt key (pronounced /ˈɔːlt/ or /ˈʌlt/) on a computer keyboard is used to change (alternate) the function of other pressed keys. Thus, the Alt key is a modifier key, used in a similar fashion to the Shift key. For example, simply pressing "A" will type the letter a, but if you hold down either Alt key while pressing A, the computer will perform an Alt+A function, which varies from program to program. The international standard ISO/IEC 9995-2 calls it Alternate key. The key is located on either side of the Space bar, but in non-US PC keyboard layouts, rather than a second Alt key, there is an 'Alt Gr' key to the right of the space bar. Both placements are in accordance with ISO/IEC 9995-2.