Must and Have To Must and Have to

Must and Have To Must and Have to are not exactly the same. We usually use must to give or ask for orders – the obligation comes from the persons who is speaking or listening. We use have to to talk about an obligation that comes from “outside” – perhaps because of the law, or a rule, or an agreement, or because some other person has given orders.

Examples I must stop smoking. (I want to) I have to stop smoking. Doctor’s orders. I can’t come to work tomorrow morning because I’ve to see the dentist. I’ve got bad toothache. I must make an appointment with the dentist. Must you wear dirty old jeans all the times? (= Is it personally important to you? ) Do you have to wear a tie at work? (= Is it a rule? )

Mustn’t and Don’t have to Mustn’t is used to tell people not to do things: it expresses “negative obligation”. (It’s prohibited = Can’t) Haven’t got to, don’t have to, don’t need to and needn’t are all used to say that something is unnecessary. They express absence of obligation: NO Obligation. You mustn’t tell Harold. (=Don’t tell Harold) You don’t have to tell Ann. (= You can if you like, but it’s not necessary) You don’t have to wear a tie at work, but you mustn’t wear jeans. (= Wear a tie or not, as you like. But NO jeans)

Have to do sth and Have sth to do Have to do something = must do something e. g. My train leaves in five minutes so I’ll have to go now. Have something to do = have something that you need or intend to do e. g. I have ten more letters to write.