(idiomatic, colloquial) Informal greeting roughly equivalent to How are you? or How's it going?

The knowledge and skill to be able to (do something correctly).

how much does it cost?

(idiomatic, informal) Why; why is it; for what reason or purpose; due to what cause?

Used to inquire about the weather. / (by extension, idiomatic) Indicating a change of subject to unimportant topics.

(rhetorical question) A general statement of surprise or bemusement with regard to a particular event.; isn't that good, or unexpected, etc.

Used literally: what length. / Used literally: what duration.

Used literally: for what duration.

(slang) how are you?

(archaic) Hello, what is that?