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

plural

whys

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.

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

That’s why I like to watch the pros.

From The Wall Street Journal • Apr. 5, 2026

"Family moviegoing is leading the industry now and these series are a lot of the reason why."

From Barron's • Apr. 5, 2026

The program is one of several reasons why Los Angeles County officials reported a double-digit reduction in the homeless mortality rate in 2024, she said.

From Los Angeles Times • Apr. 5, 2026

We asked our colleague Nadira Goffe to share her Oura Ring data with us to test out why the Trump administration is so obsessed with wearables.

From Slate • Apr. 5, 2026

“For weeks now, I have not been sleeping at nights, and do you know why this is, Elizabeth?” she said.

From "An Elephant in the Garden" by Michael Morpurgo