What does "why" mean?

1. (asking for a reason) you use this to ask for the reason or purpose of something. 2. (explaining a reason) the reason for which something happens. 3. (the reason itself) the reason or explanation for something. 4. (expressing surprise) a word used to show you are surprised or to add emphasis to what you are saying.

How do you use "why"?

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

Is it correct to say "Why you are late?"?

No — say "Why are you late?". In direct questions, the verb or auxiliary verb must come before the subject after 'why'.

why

adv. · conj. · n. · interj.

US //ˈhwaɪ// UK //wˈaɪ// why

1 asking for a reason (adv.)
A1 Beginner

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

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

Example

Why did you decide to move to a different city?

Example

Why did the board of directors choose to ignore the consultant's warnings despite the clear evidence of financial risk?
- how come
- for what reason
Pitfall

Why you are late?

Why are you late?

In direct questions, the verb or auxiliary verb must come before the subject after 'why'.
2 explaining a reason (conj.)
A2 Elementary

the reason for which something happens.

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

Example

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

Example

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

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3 the reason itself (n.)
B2 Upper Intermediate

the reason or explanation for something.

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

Example

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

Example

Before we implement the new policy, we must clearly articulate the why behind these structural changes to the staff.
4 expressing surprise (interj.)
C1 Advanced Literary Archaic

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

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

Example

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

Example

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.
- well
- indeed

Origin

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.