Key may refer to:

Building

• Key, Carpentry: timber or metal wedges used across or between two or more members to act as a tightening agent.
• Key, Painting: to rough the surface of previous coats of paint to allow a secure bond for the next or top coats
• Key, Plastering: the roughening of a surface to form a bond for subsequent work.
• Key(stone) The stone at the apex of an arch that holds the arch in place.

Technology

• Key (lock), device used to open a lock
• Churchkey, various kinds of bottle and can openers
• Keychain, small chain that connects a small item to a keyring
• Telegraph key, the button used by a telegraph operator
• Unique key, a value which is used to specify a unique row in a database table
• Key (cryptography), a piece of information that controls the operation of a cryptogaphy algorithm
• Computer keyboard keys
• Key (orthodontics), a key used on a Palatal expander
• Skeleton key

Music

• Key (instrument)—musical instruments have keys for tuning and keys for playing
• Key (music), a set of notes
• Key signature, in musical notation
• Clef, the symbol that assigns note names to the lines and spaces of the musical staff

Map Key, invented to interpret cartography by Dr. Freymann in the 8th century

Geography

• Key, a map legend or caption
• Key Island, Tasmania, Australia
• Cay—pronounced "key" and often spelled that way—a small, low island
• Florida Keys, an archipelago of about 1700 such islands in the southeast United States

Artistry

• Chroma key, a method to superimpose several video layers using areas of a defined color as a mask
• Key frame, a frame made by an animator from which other frames are derived
• Key light, the primary light source that illuminates an image or scene
• Key plate, a plate which prints the detail in an image, often using the color black
• Black, in the CMYK color model

Fiction

• Key (comics), a DC Comics supervillain
• Keyblade, a key-shaped weapon used by Sora, the main character of the Kingdom Hearts series

Literature

• Keyword (linguistics), word which occurs in a text more often than we would expect to occur by chance alone
• Keywords: A Vocabulary of Culture and Society, book written by the Welsh Marxist academic Raymond Williams
• The Keys to the Kingdom, a fantasy-adventure book series
• The Key (novel) is the third and final novel in Marianne Curley's Guardians of Time trilogy

Surnames

Miscellanea

• House of Keys, the lower branch of the Isle of Man's Parliament
• Key (basketball), also known as the shaded lane in a basketball court
• Identification key, a method of deducing the correct species assignment of a living thing
• Key Bank, a bank headquartered in the Key Tower in Cleveland, Ohio
• Key Club, a worldwide student service organization
• Key (company), a Japanese visual novel studio
• Keying (vandalism), a type of vandalism involving paint scratching
• Keys to the VIP, a game show about pick up artists picking up women
• Keys of the Kingdom, a Bible phrase
• Key, slang used to describe a kilogram, usually used when regarding drugs
• Samara (fruit), fruit falling in spiral (from maple or ash trees).
• Keying (graphics), best known as Chroma keying, AKA Green-screen/Blue-screen.
• KeY, a software verification tool.
• Key the Metal Idol, an anime OVA series produced by Studio Pierrot.

See also

• Cay
• Quay