A notched and grooved, usually metal implement that is turned to open or close a lock. A similar device used for opening or winding: the key of a clock; a can that has a key attached. A means of access, control, or possession. A vital, crucial element. A set of answers to a test. A table, gloss, or cipher for decoding or interpreting. A device, such as a wedge or pin, inserted to lock together mechanical or structural parts. Architecture The keystone in the crown of an arch. A button or lever that is depressed to operate a machine. A button that is depressed to cause a corresponding character or function to be typed or executed by a typewriter or to be accepted as input by a computer. Music A button or lever that is depressed with the finger to produce or modulate the sound of an instrument, such as a clarinet or piano. Music A tonal system consisting of seven tones in fixed relationship to a tonic, having a characteristic key signature and being the structural foundation of the bulk of Western music; tonality. Music The principal tonality of a work: an etude in the key of E. The pitch of a voice or other sound. A characteristic tone or level of intensity, as of a speech or sales campaign. Often used in combination: high-key; low-key. Botany A samara. An outline of the distinguishing characteristics of a group of organisms, used as a guide in taxonomic identification. Basketball An area at each end of the court between the base line and the foul line and including the jump-ball circle at the foul line: a jump shot from the top of the key. Of crucial importance; significant: key decisions; the key element of the thesis. To lock with or as if with a key. Architecture To furnish (an arch) with a keystone. Music To regulate the pitch of. To bring into harmony; adjust or adapt. To supply an explanatory key for. To operate (a device), as for typesetting, by means of a keyboard.