why and why not

Replies

We generally use Why not?, not Why?, in short replies to negative statements. Compare:

• ‘They’ve decided to move to Devon.’ ‘Why?’
• ‘I can’t manage tomorrow evening.’ ‘Why not?’ (More natural than Why?)

Why not? can also be used to agree to a suggestion.

• ‘Let’s eat out this evening.’ ‘Yes, why not?’

Why should …?

A structure with why followed by should can suggest surprise.

• I wonder why she should want to go out with me.

The structure can also suggest anger or refusal to do something.

• I don’t see why we should have to pay for your mistake.
• ‘Give me a cigarette.’ ‘Why should I?’

note

For a similar structure with how, (see here).

Infinitive structures

Why can be followed by an infinitive without to. This structure can suggest that an action is unnecessary or pointless.

• Why argue with him? He’ll never change his mind. (not Why arguing …?) or Why to argue …?
• Why pay more at other shops? We have the best value.

Why not + infinitive without to is used to make suggestions.

• ‘Sandy’s in a bad mood.’ ‘Why not give her some flowers?’

Why don’t …? can be used in the same way.

• Why don’t you give her some flowers?
• Why don’t we go and see Julie?