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

Felix Salmon, Elizabeth Spiers, and Emily Peck explain why this absurd-sounding venture is actually a pretty clever piece of financial engineering.

From Slate • Apr. 18, 2026

But Chris Conway said he could "understand why" the decision was made, which followed concerns over roadworks near Grand Central Station.

From BBC • Apr. 18, 2026

That’s why Wolfe Research chief investment strategist Chris Senyek screened for some.

From Barron's • Apr. 17, 2026

In a wide-ranging interview with architecture critic Sam Lubell, Peter Zumthor talks about the evolution of LACMA’s new David Geffen Galleries, how L.A. changed his practice, and why certain criticisms of the building are overblown.

From Los Angeles Times • Apr. 17, 2026

She interrupts me a lot, sometimes asking me to repeat something I said, and sometimes it’s with another question aimed at clarifying how and why certain things happened.

From "Red Flags and Butterflies" by Sheryl Azzam