From Middle English why, from Old English hwȳ, hwī (“why”, literally “by what, for what”), from Proto-Germanic *hwī (“by what, how”), from Proto-Indo-European *kʷey, instrumental case of *kʷis (“who”), *kʷid (“what”). Cognate with Old Saxon hwī (“why”), hwiu (“how; why”), Middle High German wiu (“how, why”), archaic Danish and Norwegian Bokmål hvi (“why”), Norwegian Nynorsk kvi (“why”), Swedish vi (“why”), Faroese and Icelandic hví (“why”), Latin quī (“why”), Ancient Greek πεῖ (peî, “where”). Compare Old English þȳ (“because, since, on that account, therefore, then”, literally “by that, for that”). See thy.
why (not comparable)
- For what cause, reason, or purpose (interrogative adverb).
- Introducing a complete question.
- Introducing a verb phrase (bare infinitive clause).
- Introducing a noun or other phrase.
- For which cause, reason, or purpose (relative adverb).
why (plural whys)
- An exclamation used to express indignation, mild surprise, or impatience.
why (plural whies)
- (Britain, dialectal) A young heifer.