Synonyms

why

American

[hwahy, wahy] / ʰwaɪ, waɪ /

adverb

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

Why did you behave so badly?

conjunction

for what cause or reason.

I don't know why he is leaving.
for which; on account of which (usually after reason to introduce a relative clause).

the reason why he refused to go.
the reason for which.

That is why he returned.

noun

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

a child's unending hows and whys.
the cause or reason.

the whys and wherefores of a troublesome situation.

interjection

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

Why, it's all gone!

why British

/ waɪ /

adverb

1. for what reason, purpose, or cause?
  
  why are you here?
2. ( used in indirect questions )
  
  tell me why you're here

"Collins English Dictionary — Complete & Unabridged" 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

pronoun

for or because of which

there is no reason why he shouldn't come

"Collins English Dictionary — Complete & Unabridged" 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

noun

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

"Collins English Dictionary — Complete & Unabridged" 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

interjection

an introductory expression of surprise, disagreement, indignation, etc

why, don't be silly!

"Collins English Dictionary — Complete & Unabridged" 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

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

Vocabulary lists containing why

Scrabble: Words with no Vowels

Looking to grow your vocabulary? Check out this interactive, curated word list from our team of English language specialists at Vocabulary.com – one of over 17,000 lists we've built to help learners worldwide!

Example Sentences

Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.

The task force hopes to uncover trends and better understand why the water continues to be contaminated in the area.

From Los Angeles Times • May 20, 2026

If voluntarily storing information with Google destroys Fourth Amendment protection, he suggested, why would the same logic not apply to email, documents, cloud photographs, or calendars?

From Slate • May 20, 2026

The reasons why Fidel Castro's government decided to shoot down the planes are still the subject of debate.

From BBC • May 20, 2026

The Wall Street Journal talked to Chesky about the hotel push, AI’s potential and why the World Cup validates its strategy.

From The Wall Street Journal • May 20, 2026

Money . . . why, that belonged to the world of shops and trolley cars.

From "The Hiding Place" by Corrie ten Boom

Definitions and idiom definitions from Dictionary.com Unabridged, based on the Random House Unabridged Dictionary, © Random House, Inc. 2023