key

Concise Oxford English Dictionary © 2008 Oxford University Press:
key1

▶noun (pl. keys)

• 1 a small piece of shaped metal with incisions cut to fit the wards of a particular lock, which is inserted into the lock and rotated to open or close it or to operate a switch.

  ■ an instrument for grasping and turning a screw, peg, or nut.

  ■ a pin, bolt, or wedge inserted into a hole or between parts so as to lock the parts together.

• 2 a lever depressed by the finger in playing an instrument such as the organ, piano, flute, or concertina.

• 3 each of several buttons on a panel for operating a typewriter, word processor, or computer terminal.

• 4 a lever operating a mechanical device for making or breaking an electric circuit.

• 5 a thing that provides access to or understanding of something: a key to success.

  ■ an explanatory list of symbols used in a map or table.

  ■ a set of answers to exercises or problems.

  ■ a word or system for solving a cipher or code.

  ■ the first move in the solution of a chess problem.

• 6 Music a group of notes based on a particular note and comprising a scale, regarded as forming the tonal basis of a passage of music.

  ■ the tone or pitch of someone's voice.

• 7 the dry winged fruit of an ash, maple, or sycamore; a samara.

• 8 roughness on a surface, provided to assist adhesion of plaster or other material.

• 9 Basketball the keyhole-shaped area marked on the court near each basket.

▶adjective of crucial importance: a key figure. ▶verb (keys, keying, keyed)

• 1 enter or operate on (data) by means of a computer keyboard.

• 2 fasten into position with a pin, wedge, or bolt.

• 3 (key to) chiefly N. Amer. link with.

  ■ (key into/in with) be connected or in harmony with.

• 4 (be keyed up) be nervous, tense, or excited.

• 5 roughen (a surface) to assist adhesion of plaster or other material.

– phrases
in (or out of) key in (or out of) harmony.

– derivatives
keyed adjective,
keyer noun,
keyless adjective.

– origin OE cǣg, cǣge, of unknown origin.

Concise Oxford English Dictionary © 2008 Oxford University Press:
key2

▶noun a low-lying island or reef, especially off the coast of Florida or in the Caribbean.

– origin C17: from Sp. cayo ‘reef’, influenced by quay.