Yes, key is a Scrabble word!

Verb

1. Identify as in botany or biology, for example

2. Provide with a key

3. Vandalize a car by scratching the sides with a key

4. Regulate the musical pitch of

5. Harmonize with or adjust to

Adjective

1. Serving as an essential component

Noun

1. Metal device shaped in such a way that when it is inserted into the appropriate lock the lock's mechanism can be rotated

2. Something crucial for explaining

3. Pitch of the voice

4. Any of 24 major or minor diatonic scales that provide the tonal framework for a piece of music

5. A kilogram of a narcotic drug

6. A winged often one-seed indehiscent fruit as of the ash or elm or maple

7. United States lawyer and poet who wrote a poem after witnessing the British attack on Baltimore during the War of 1812; the poem was later set to music and entitled `The Star-Spangled Banner' (1779-1843)

8. A coral reef off the southern coast of Florida

9. (basketball) a space (including the foul line) in front of the basket at each end of a basketball court; usually painted a different color from the rest of the court

10. A list of answers to a test

11. A list of words or phrases that explain symbols or abbreviations

12. A generic term for any device whose possession entitles the holder to a means of access

13. Mechanical device used to wind another device that is driven by a spring (as a clock)

14. The central building block at the top of an arch or vault

15. A lever (as in a keyboard) that actuates a mechanism when depressed