why adverb [OE. whi, why, AS. hwī, hw, instrumental case of hwā, hwæt; akin to Icel. hvī why, Dan. & Sw. hvi; cf. Goth. hw. . See Who.]

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

Turn ye, turn ye from your evil ways; for why will ye die, O house of Israel? Ezek. xxxiii. 11.

2. For which; on account of which; – used relatively.

No ground of enmity between us known
Why he should mean me ill or seek to harm. Milton.

Turn the discourse; I have a reason why
I would not have you speak so tenderly. Dryden.

3. 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.

☞ Why is sometimes used as an interjection or an expletive in expression of surprise or content at a turn of affairs; used also in calling.

“Why, Jessica!” Shak.

If her chill heart I can not move,
Why, I’ll enjoy the very love. Cowley.

Sometimes, also, it is used as a noun.

The how and the why and the where. Goldsmith.

For why

because; why. See For

why [Obs. or Colloq.]Why, noun A young heifer. [Prov. Eng.] Grose.