key

1. 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). (countable) · This key is to the backdoor.· insert the key into the lock (formal); put the key in the lock (informal)
2. A card or fob that electronically signals a lock to open. (countable) · My hotel room key is a card.· The gym will give you a fob that opens the door.
3. A piece of information (e.g., a password or passphrase) used to encode or decode a message or messages. (countable, figuratively)
4. A password restricting access to an IRC channel. (countable)
5. A key bump (A portion of a recreational drug in powdered form that is snorted from a key or similar small object.) (countable, slang) · I saw him snort a key at the party.
6. 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. (countable) · The exterminator will bring a key thingy that can open the bait boxes.· Safe-deposit boxes open with a special key.
7. A cotter pin.
8. A piece of wood used as a wedge.

Plural keys