Unit 7

Have to, don't have to

EXAMPLES

[+]
I have to speak English at work.
She has to get up at seven every day.
[–]
We don't have to wear a uniform at this school.
He doesn't have to work on Saturdays.
[?]
Do I have to buy a grammar book?
What time does she have to get up in the morning?

FORM

• We use have to + verb (infinitive) to talk about rules and obligations.
• We use don't have to + verb (infinitive) to say that there is no obligation or that something is not necessary.
• We use do / does to make questions and negatives.
  Do I have to go? NOT Have I to go?
• We don't contract have or has.
  I have to go. NOT I've to go.

Must / mustn't

EXAMPLES

[+]
You must do your homework tonight.
She must tidy her room before she goes out.
[–]
You mustn't leave your bags here. (mustn't = must not)
I mustn't forget to call her tonight.
[?]
Must I go to bed now?
When must we decide about the party?

FORM

• We use must + verb (infinitive without to) to talk about rules and obligations.
• Must / musn't are the same for all persons.
• We use mustn't + verb (infinitive without to) to say that something is prohibited.