why

American  

[hwahy, wahy] / ʰwaɪ, waɪ /

adverb

1. for what? for what reason, cause, or purpose?.

   Why did you behave so badly?

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conjunction

1. for what cause or reason.

   I don't know why he is leaving.

2. for which; on account of which (usually after reason to introduce a relative clause).

   the reason why he refused to go.

3. the reason for which.

   That is why he returned.

noun

• whys
  plural

1. a question concerning the cause or reason for which something is done, achieved, etc..

   a child's unending hows and whys.

2. the cause or reason.

   the whys and wherefores of a troublesome situation.

interjection

1. (used as an expression of surprise, hesitation, etc., or sometimes a mere expletive).

   Why, it's all gone!

why British  

/ waɪ /

adverb

1. 1. for what reason, purpose, or cause?

      why are you here?

   2. ( used in indirect questions )

      tell me why you're here

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pronoun

1. for or because of which

   there is no reason why he shouldn't come

noun

1. (usually plural) the reason, purpose, or cause of something (esp in the phrase the whys and wherefores )

interjection

1. an introductory expression of surprise, disagreement, indignation, etc

   why, don't be silly!

Usage

See reason.

Other Word Forms

Noun Inflected Forms

• whys
  plural

Etymology

Origin of why

First recorded before 900; Middle English; Old English hwī, hwȳ, instrumental case of hwæt what; cognate with Old Norse hvī

Example Sentences

See Examples For:

why whys

"This is why street performers often have to face municipal and police regulations governing public spaces, as well as state-specific anti-begging laws," says lawyer Kaushik Mitra.

From BBC ● Oct. 2, 2026

So with this year’s tremendous increase in long-term interest rates as the bond market has sold off, you might be wondering why the stock market hasn’t declined.

From MarketWatch ● Oct. 2, 2026

These records of AI agents’ inner thoughts constitute much of the evidence of why they go rogue.

From The Wall Street Journal ● Oct. 2, 2026

RTX won more missile business, so why isn’t the stock budging?

From Barron's ● Oct. 2, 2026

This was why I’d come here, for this feeling, this lightness.

From "Legendary Frybread Drive-In" by Cynthia Leitich Smith

One note for Miles, like Billie Holiday, like Cindy says, that’s enough to understand all the whys and all the reasons why it’s sacred to be alive.

From Los Angeles Times ● May 25, 2026

Players for the fourth-seeded Reign shared their individual whys that propelled them to the club’s first championship final since 2015.

From Seattle Times ● Nov. 11, 2023

So this book goes into all the whys.

From Salon ● Oct. 31, 2023

Physicists believe that there must have been some primordial imbalance that allowed matter to dominate the universe, yet the hows and whys remain open questions.

From Scientific American ● Sep. 27, 2023

“What you should know is that I’m concerned. Knowing what I was like at your age, I’m real curious about the whys of the trouble you been in.”

From "Clean Getaway" by Nic Stone