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Etymology 1

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). 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)

  1. For what cause, reason, or purpose (interrogative adverb).
    1. Introducing a complete question.
      Why is the sky blue?
      Why did you do that?
      I don’t know why he did that
      Tell me why the moon changes phase.
    2. Introducing a verb phrase (bare infinitive clause).
      Why spend money on something you already get for free?
      Why not tell him how you feel?
    3. Introducing a noun or other phrase.
      Why him? Why not someone taller?
  2. For which cause, reason, or purpose (relative adverb).
    That's the reason why I did that.
    • (deprecated use of |lang= parameter)
      2013 July 20, “Welcome to the plastisphere”, in The Economist, volume 408, number 8845:
      Plastics are energy-rich substances, which is why many of them burn so readily. Any organism that could unlock and use that energy would do well in the Anthropocene. Terrestrial bacteria and fungi which can manage this trick are already familiar to experts in the field.
The translations below need to be checked and inserted above into the appropriate translation tables, removing any numbers. Numbers do not necessarily match those in definitions. See instructions at Wiktionary:Entry layout § Translations.


why (plural whys)

  1. reason
    A good article will cover the who, the what, the when, the where, the why and the how.



  1. An exclamation used to express indignation, mild surprise, or impatience.
    • Daniel Defoe
      Why, child, I tell thee if I was thy mother I would not disown thee; don't you see I am as kind to you as if I was your mother?”
Derived terms

Etymology 2


why (plural whies)

  1. (Britain, dialect) A young heifer.
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Further reading






  1. (Standard Cornish, Standard Written Form) you (formal or plural)