Material unit 2

must / have 

Use

We use must to talk about a personal feeling of obligation to do something.

I must remember to post the letter today.

You must phone your grandmother tonight.

We use have to to talk about an obligation that is a fact, or a rule or law.

You have to be sixteen before you can leave school.

We have to revise for our exams next week.

We use don’t have to/doesn’t have to to talk about something that is not an obligation.

You don’t have to do any homework tonight.

We use mustn’t to say that something is prohibited.

You mustn’t smoke in this area.

We use had to to talk about a past obligation.

We had to get up at five o’clock this morning.

Form

must / mustn’t + infinitive

I must phone Sarah tonight.

have to / don’t have to / doesn’t have to

+ infinitive

We don’t have to get up early tomorrow.

had to + infinitive

John had to help his mother yesterday.