Key

noun (1)

1. a usually metal instrument that is used to open a lock or to start or access a mechanism
2. a part to be depressed by a finger that serves as one unit of a keyboard
3. a representation of such a key (such as a space delineated on a touch screen)also
4. one of the levers of a keyboard musical instrument that actuates the mechanism and produces the tones
5. a lever that controls a vent in the side of a woodwind instrument or a valve in a brass instrument
6. a system of tones and harmonies generated from a hierarchical scale of seven tones based on a tonic
7. characteristic style or tone
8. the tone or pitch of a voice
9. the predominant tone of a photograph with respect to its lightness or darkness
10. a decoration or charm resembling a key
11. a small switch for opening or closing an electric circuit
12. the set of instructions governing the encipherment and decipherment of messages
13. something that resembles a key in form or function
14. see also key card, key fob
15. a free-throw area in basketball : free throw lane
16. cotter pin
17. cotter
18. a keystone in an arch
19. a small piece of wood or metal used as a wedge or for preventing motion between parts
20. samara
21. Francis Scott 1779–1843 American lawyer and author of "The Star-Spangled Banner"
22. a means of gaining or preventing entrance, possession, or control
23. an instrumental or deciding factor
24. something that gives an explanation or identification or provides a solution
25. a list of words or phrases giving an explanation of symbols or abbreviations
26. an aid to interpretation or identification : clue
27. an arrangement of the salient characters of a group of plants or animals or of taxa designed to facilitate identification
28. a map legend