(1):

(adv.) For what cause, reason, or purpose; on what account; wherefore; - used interrogatively. See the Note under What, pron., 1.

(2):

(adv.) For which; on account of which; - used relatively.

(3):

(adv.) The reason or cause for which; that on account of which; on what account; as, I know not why he left town so suddenly; - used as a compound relative.

(4):

(n.) A young heifer.