Meta key

The Meta key is a modifier key on certain keyboards, specifically MIT and Lisp machine keyboards and successors, such as the Knight keyboard, space-cadet keyboard (where it is labeled “META”), Symbolics keyboards (where it is labeled “META” or “Meta”), and on Sun Microsystems keyboards (where it is marked as a solid diamond “◆”).

On keyboards that lack a physical Meta key (or keys), its functionality may be invokable by other keys such as the Alt key, the Windows key, or user-configured keys. If no Meta key function is available, some software will accept alternate keybindings using, for example, the Esc key as a prefix key (as, for example, in Emacs).

On some systems the Meta modifier may be used in a manner similar to Macintosh's Command key, but has been used in other ways, including as a user-configurable modifier in the X Window System, or in combination with other modifier keys such as Hyper and Super, also seen on the classic Lisp keyboards and supported by windows systems such as X.

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