An object designed to open and close a lock or to activate or deactivate something, especially a length of metal inserted into a narrow opening on the lock to which it is matched (keyed). • A card or fob that electronically signals a lock to open. • A piece of information (e.g., a password or passphrase) used to encode or decode a message or messages. • A password restricting access to an IRC channel. • A key bump (A portion of a recreational drug in powdered form that is snorted from a key or similar small object.) • Any of various tools comparable to a wrench (spanner) or driver, which have a specialized end that matches a fixture, analogously to a lock's key. • An object designed to fit between two other objects (such as a shaft and a wheel) in a mechanism and maintain their relative orientation. • A cotter pin. • A piece of wood used as a wedge. • The last board of a floor when laid down. • A keystone. • That part of the plastering which is forced through between the laths and that holds the rest in place. • A wooden wedge, driven sideways between a bullhead rail and a cast-iron chair, to keep the rail securely in position. • A crucial step or requirement. • An idea, theory or observation that explains, justifies or renders (something) comprehensible. • A deciding factor. • Senses relating to a guide that identifies information. • A small guide explaining symbols, abbreviations or terminology, especially the legend on a map or chart. • A guide to the correct answers of a worksheet or test. • A series of logically organized groups of discriminating information which aims to allow the user to correctly identify a taxon; a taxonomic key. • A value that uniquely identifies an entry in a container. • In a relational database, a field used as an index into another table (not necessarily unique). • Senses relating to a set of features that modify the output of a device. • One of several small, usually square buttons on a typewriter or computer keyboard, mostly corresponding to text characters. • In musical instruments, one of the valve levers used to select notes, such as a lever opening a hole on a woodwind. • In instruments with a keyboard such as an organ or piano, one of the levers, or especially the exposed front end of it, which are depressed to cause a particular sound or note to be produced. • A scale or group of pitches constituting the basis of a musical composition. • The lowest note of a scale; keynote. • In musical theory, the total melodic and harmonic relations, which exist between the tones of an ideal scale, major or minor; tonality. • In musical theory and notation, the tonality centering in a given tone, or the several tones taken collectively, of a given scale, major or minor. • In musical notation, a sign at the head of a staff indicating the musical key. • The general pitch or tone of a sentence or utterance. • A modification of an advertisement so as to target a particular group or demographic. • Senses of items with visual similarity to a key or group of keys on a keyring. • An item of decor shaped like a key. • An indehiscent, one-seeded fruit furnished with a wing, such as the fruit of the ash and maple; a samara. • The free-throw lane together with the circle surrounding the free-throw line, the free-throw lane having formerly been narrower, giving the area the shape of a skeleton key hole. • The thirty-third card of the Lenormand deck, which features an image of a key. • Senses related to colors. • The overall color tone of a painting or other visual art, with a high key indicating generally light colors and a low key indicating generally dark colors. • The black ink layer, especially in relation to the three color layers of cyan, magenta, and yellow. See also CMYK. • A color to be masked or made transparent. • A manual electrical switching device primarily used for the transmission of Morse code. • The degree of roughness, or the ability of a surface to retain an applied liquid, such as paint or glue.