Emily Dickinson Lexicon

KEY, n.¹ [kē. Sax. cæg.]

1. In a general sense, a fastener; that which fastens; as, a piece of wood in the frame of a building, or in a chain, &c.
2. An instrument for shutting or opening a lock, by pushing the bolt one way or the other. Keys are of various forms, and fitted to the wards of the locks to which they belong.
3. An instrument by which something is screwed or turned; as, the key of a watch or other chronometer.
4. The stone which binds an arch. [See Key-stone.]
5. In an organ or harpsichord, the key, or finger key, is a little lever or piece in the fore part by which the instrument is played on by the fingers.
6. In music, the key, or key note, is the fundamental note or tone to which the whole piece is accommodated, and with which it usually begins and always ends. There are two keys, one of the major, and one of the minor mode. Key sometimes signifies a scale or system of intervals. – Rousseau.
7. An index, or that which serves to explain a cipher. Hence,
8. That which serves to explain any thing difficult to be understood.
9. In the Romish church, ecclesiastical jurisdiction, or the power of the pope; or the power of excommunicating or absolving. – Encyc.
10. A ledge or lay of rocks near the surface of the water.
11. The husk containing the seed of an ash. – Evelyn.