Have to, don't have to, must, mustn't

Use must + infinitive without to

Must is a modal verb, and modal verbs are followed by an infinitive without to.

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I must go to the doctor. (NOT I must lớn go khổng lồ the doctor.)No -s

Modal verbs don’t add -s after he/she/it.

He must come with us. (NOT He must comes with us.)Use must/mustn’t in negatives and questions

Must is an auxiliary verb. This means that it has a negative và an interrogative form. Vị not use do/did in negatives và questions.

We mustn’t arrive early. (NOT We don’t must arrive early.)Must we arrive early? (NOT bởi we must arrive early?)

have to/don’t have to

Use do and did in negatives and questions

The verb have in have to is not an auxiliary verb. Use do/don’t, does/doesn’t, did/didn’t in questions and negative sentences in present and past.

Do you have to get up early tomorrow? (NOT Have you to get up early tomorrow?)Did you have to buy a new sound card?We don’t have to stay until the end.No contraction

The verb have in have to cannot be contracted lớn ‘ve.

I have to lớn study for the exam tomorrow. (NOT I’ve khổng lồ study for the exam tomorrow.)Past và future forms

Only have to has a past and a future form. Must does not have a past or a future form.

Yesterday, I had to take a taxi. (NOT Yesterday, I must take a taxi)You will have to take a taxi if it rains tomorrow. (NOT You will must take a taxi.)

must vs have to / mustn’t vs don’t have to – meaning


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have to

Rules and obligations

We use have to to lớn talk about rules & obligations, something that is necessary.

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I have lớn get to work before 7 tomorrow.The car broke down & we had lớn call a taxi.


Rules & obligations

Must is very similar to have to. We use must + infinitive (without to) khổng lồ talk about rules and obligations.

I must go khổng lồ the doctor.I must get up early tomorrow.

don’t have to

Don’t need lớn – not necessary

If you don’t have to bởi something, it means that you ‘don’t need to’ vị something (there is no obligation). You can do it but you don’t need to vày it if you don’t want to vày it.

You don’t have to pick me up at the station. I can take a taxi. (=You can pick me up, but you don’t need to bởi it).



Use mustn’t lớn talk about something that you can’t do. It’s necessary that you don’t vị it.

You mustn’t call me before 8. (=You can’t điện thoại tư vấn me before 8.)I mustn’t lose my concentration now.

must vs have to


Obligation from the speaker

We normally use must when lớn talk about obligations that come from the opinion of the speaker. The speaker thinks it’s necessary or important to vị something.

MANAGER: You must get up early tomorrow. The meeting is at nine. (=The obligation comes from the manager. The manager thinks it’s necessary.)DOCTOR: You must stop smoking. (=It’s the doctor’s opinion. The doctor thinks it’s necessary.)SMOKER: I must stop smoking. (=It’s the smoker’s opinion. The smoker thinks it’s necessary khổng lồ stop smoking.)

have to

External obligation

We normally use have to when there’s an external obligation. The obligation doesn’t come from the speaker’s opinion; another person thinks it’s necessary.

WORKER: We have to get up early tomorrow. The meeting is at nine. (=The obligation comes from the manager, not from the worker.)SMOKER: I have lớn stop smoking. (=It’s the doctor’s opinion, not the smoker’s opinion. The doctor thinks it’s necessary.)

mustn’t vs don’t have to

don’t have to

You don’t need to vì chưng it; not necessary; no obligation

Don’t have tomustn’t have opposite meanings. We say that we don’t have to bởi something when we don’t need to vì something; we can vì it, but it’s not necessary.

You don’t have lớn wait here. (=You can vị it, but it’s not necessary)


Prohibition; it’s necessary that you don’t vày it

We say that we mustn’t do something when we cannot bởi something; it is necessary that we don’t bởi something.