key

(noun) metal device shaped in such a way that when it is inserted into the appropriate lock the lock's mechanism can be rotated.

(noun) something crucial for explaining. Examples: "The key to development is economic integration."

(noun) pitch of the voice. Examples: "He spoke in a low key."

(noun) any of 24 major or minor diatonic scales that provide the tonal framework for a piece of music. Synonyms: tonality.

(noun) a kilogram of a narcotic drug. Examples: "They were carrying two keys of heroin."

(noun) a winged often one-seed indehiscent fruit as of the ash or elm or maple. Synonyms: samara, key fruit.

(noun) 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). Synonyms: Key, Francis Scott Key.

(noun) a coral reef off the southern coast of Florida. Synonyms: cay, Florida key.

(noun) (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. Synonyms: paint. Examples: "He hit a jump shot from the top of the key." "He dominates play in the paint."

(noun) a list of answers to a test. Examples: "Some students had stolen the key to the final exam."

(noun) a list of words or phrases that explain symbols or abbreviations.

(noun) a generic term for any device whose possession entitles the holder to a means of access. Examples: "A safe-deposit box usually requires two keys to open it."

(noun) mechanical device used to wind another device that is driven by a spring (as a clock). Synonyms: winder.

(noun) the central building block at the top of an arch or vault. Synonyms: keystone, headstone.

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

(verb) identify as in botany or biology, for example. Synonyms: identify, discover, key out, distinguish, describe, name.

(verb) provide with a key. Examples: "We were keyed after the locks were changed in the building."

(verb) vandalize a car by scratching the sides with a key. Examples: "His new mercedes was keyed last night in the parking lot."

(verb) regulate the musical pitch of.

(verb) harmonize with or adjust to. Examples: "Key one's actions to the voters' prevailing attitude."

(adj) serving as an essential component. Synonyms: cardinal, central, fundamental, primal. Examples: "A cardinal rule." "The central cause of the problem." "An example that was fundamental to the argument." "Computers are fundamental to modern industrial structure."