key [-s] n

OE cæg.

  1. Piano component; ivory lever on the front board of an organ, pianoforte, etc.; segment of a musical instrument which the player presses down to produce musical notes; [fig.] aspect of being.
  2. Fundamental note; basic tone of a piece of music; [metaphor] song; hymn; anthem.
  3. Tool for release; instrument of access; mechanism for unsealing a casket; [fig.] assess; control; power of custody; admission by possession of the keys of any place.
  4. Connection; emblem; symbol; sign; signal; thing that opens or closes the way to something.

key [-s] n

OFr kay

  1. Ledge; reef; bank; geographical formation; [fig.] index; explanation; answer for anything difficult to understand; [word play] kind of music; musical register.