Why

Webster's Dictionary of the English Language

·noun A young heifer.

II. Why ·adv For which; on account of which;

— used relatively.

III. Why ·adv For what cause, reason, or purpose; on what account; wherefore;

— used interrogatively. ·see the Note under What, ·pron, 1.

IV. Why ·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.