Why

Why is a wh-word. We use why to talk about reasons and explanations.

Why as a question word

We can use why to ask about reasons and explanations:

Why did he leave home when he was 16?

Why didn’t you tell Gemma?

Why is the Earth round?

We can use why in indirect questions:

He asked me why I wanted to leave the job.

I wonder why he told nobody he was getting married.

We can use why on its own as a response:

A:
I’m going home now.

B:
Why?

When we reply to a negative statement, we usually say why not?:

A:
I don’t like it here.

B:
Why not?

When we ask for reasons in speaking, we can use the phrase why is that? In informal conversations we often say why’s that?:

A:
Look, the moth is attracted to the light.

B:
Why is that?

A:
I’m not sure.

A:
She’s not going to college this year.

B:
Why’s that?

A:
She says she wants to travel for a while.

We can use why ever or why on earth to add emphasis and to show shock or surprise. We usually stress ever and earth:

A:
Beth has decided to go on holiday by herself this year.

B:
Why everwould anyone want to go on holiday alone?

Why on earth has Julie bought me this expensive present?

In informal contexts we sometimes use what for? with the same meaning of asking for a reason:

A:
Ann’s going to be really upset with me.

B:
What for?

A:
I forgot to call her back last night.

Warning:

We don’t use why as a conjunction when we mean because:

I’m going home now because I’m tired.

Not: … why I’m tired.

We often use the phrase that’s why to give a reason:

A:
Frank and Ellen have three children now.

B:
That’s whythey moved house. They needed more space.

A:
Ian’s not been feeling well recently, has he?

B:
No. That’s whyhe’s taken some time off.

When we are annoyed about something, we sometimes use the phrase why should:

Why should taxpayers have to pay more because the government has not managed its spending properly?

Why should old people have to worry about health insurance?

Why should I? as a response is very direct and rude:

[A is a mother and B is a child who is opening and closing the car window]

A:
Stop doing that.

B:
Why should I?

We use why don’t and why not to make suggestions:

Why don’t we leave the washing-up until tomorrow morning? It’s too late now. (or Why notleave the washing up …)

We can use the phrase why not? as a reply which shows that we agree to a suggestion or request:

A:
How about we invite Barbara and Gina round on Saturday night?

B:
Why not? We haven’t seen them in a long time.

Be careful not to use why instead of because:

I have not placed an order for a long time because I am unhappy with the last delivery.

Not: I have not placed an order for a long time why I am unhappy …