definition of
key

[1] #1 key n. metal device shaped in such a way that when it is inserted into the appropriate lock the lock's mechanism can be rotated. wn

[2] #2 key s. [cardinal, central, fundamental, primal] serving as an essential component; "a cardinal rule"; "the central cause of the problem"; "an example that was fundamental to the argument"; "computers are fundamental to modern industrial structure". wn

[3] #3 key n. something crucial for explaining; "the key to development is economic integration". wn

[4] #4 key n. pitch of the voice; "he spoke in a low key". wn

[5] #5 key v. [identify, discover, key out, distinguish, describe, name] identify as in botany or biology, for example. wn