English definition of “key”
/kiː/ noun [C]
FOR LOCKS › a piece of metal cut into a particular shape and used for locking things such as doors, or for starting an engine: I've lost my car keys.
METHOD › a way of explaining or achieving something: Hard work is the key to success.
KEYBOARD › one of the parts you press with your fingers on a keyboard or musical instrument to produce letters, numbers, or to make a sound
MUSIC › a set of musical notes based on one particular note: the key of D major
SYMBOLS › a list which explains the symbols on a map or picture