English Reference

Word

why

US/ˈhwaɪ/

UK/wˈaɪ/

Definitions

01asking for a reason

A1 · Beginner

adv. you use this to ask for the reason or purpose of something.

adv. used as an interrogative adverb to inquire about the cause, reason, or purpose of an action.

“Why did you decide to move to a different city?”

“Why did the board of directors choose to ignore the consultant's warnings despite the clear evidence of financial risk?”

Pitfall

Why you are late?

Why are you late?

In direct questions, the verb or auxiliary verb must come before the subject after 'why'.

Synonyms

how comefor what reason

02explaining a reason

A2 · Elementary

conj. the reason for which something happens.

conj. used as a relative adverb to introduce a subordinate clause that explains a reason.

“I do not know why the car is making that strange noise.”

“The primary reason why the project failed was a lack of communication between the design and engineering departments.”

Synonyms

the reason that

03the reason itself

B2 · Upper Intermediate Countable noun

n. the reason or explanation for something.

n. the underlying reason or cause for a situation, often paired with 'how' or 'wherefore'.

“The book explains the why and how of the French Revolution.”

“Before we implement the new policy, we must clearly articulate the why behind these structural changes to the staff.”

Synonyms

reasoncauseexplanation

04expressing surprise

C1 · Advanced Literary · Archaic

interj. a word used to show you are surprised or to add emphasis to what you are saying.

interj. used to express mild surprise, hesitation, or to emphasize a following statement.

“Why, I had no idea you were planning to visit us today.”

“Why, it has been nearly twenty years since we last walked through these gardens together.”

Usage

Often placed at the beginning of a sentence to signal a shift in thought or a reaction to new information.

Synonyms

wellindeed

Etymology

From Middle English why, from Old English hwȳ (“why”), from Proto-Germanic hwī (“by what, how”), from Proto-Indo-European kʷey, instrumental case of kʷís (“who”), kʷid (“what”). 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”), Doric Greek πεῖ (peî, “where”), Ukrainian чи (čy, “if”), Polish czy, Czech či (“or”), Serbo-Croatian či (“if”). Compare Old English þȳ (“because, since, on that account, therefore, then”, literally “by that, for that”). See thy.

Etymology adapted from Wiktionary, available under CC BY-SA 4.0.

This entry

Exam level
CambridgeCambridgeCambridge English QualificationsThe exam suite from Cambridge University Press & Assessment, from A1 Movers up to C2 Proficiency. The benchmark names double as CEFR labels.A1 MoversIELTSIELTSInternational English Language Testing SystemThe 0–9 band test co-owned by the British Council, IDP, and Cambridge. Used for university entry, work, and migration.2.0–3.0TOEFL iBTTOEFL iBTTest of English as a Foreign Language, Internet-Based TestETS's academic English test, the standard route for US university admissions. Scored 0–120, with a 1–6 scale since 2026.1–6 scale: 1.0–1.50–23TOEICTOEICTest of English for International CommunicationETS's workplace English test, big in Japan and Korea. Listening & Reading scores 10–990 and tops out at C1.120–224
Frequency
Very common
Level
A1 · BeginnerOxford
Updated

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