Definitions from Wiktionary ( )

▸ adverb:  (interrogative) For what cause, reason, or purpose.
▸ adverb:  Introducing a complete question.
▸ adverb:  With a negative, used rhetorically to make a suggestion.
▸ adverb:  Introducing a verb phrase (bare infinitive clause).
▸ adverb:  Introducing a noun or other phrase.
▸ adverb:  (relative) For which cause, reason, or purpose.
▸ adverb:  (fused relative) The cause, reason, or purpose for which.
▸ noun:  Reason.
▸ verb:  (intransitive, transitive) To ask (someone) the question "why?".
▸ noun:  (UK, dialect, archaic) A young heifer.
▸ noun:  Alternative form of wye; the name of the Latin-script letter Y/y. [The name of the Latin-script letter Y/y.]

---

▸ Word origin

▸ Words similar to why
▸ Usage examples for why

▸ Idioms related to why
▸ Wikipedia articles (New!)
▸ Popular adjectives describing why
▸ Words that often appear near why
▸ Rhymes of why

▸ Invented words related to why