Have to (objective obligation)
We often use have to to say that something is obligatory, for example:
• Children have to go to school.
Structure of Have to
Have to is often grouped with modal auxiliary verbs for convenience, but in fact it is not a modal verb. It is not even an auxiliary verb. In the have to structure, "have" is a main verb. The structure is:
subject + auxiliary verb + have + infinitive (with to)
Look at these examples in the simple tense:
subject auxiliary verb main verb have infinitive (with to)
+ She has to work.
- I do not have to see the doctor.
Did you have to go to school?
Use of Have to
In general, have to expresses impersonal obligation. The subject of have to is obliged or forced to act by a separate, external power (for example, the Law or school rules). Have to is objective. Look at these examples:
• In France, you have to drive on the right.
• In England, most schoolchildren have to wear a uniform.
• John has to wear a tie at work.
In each of the above cases, the obligation is not the subject's opinion or idea. The obligation is imposed from outside.
We can use have to in all tenses, and also with modal auxiliaries. We conjugate it just like any other main verb. Here are some examples:
subject auxiliary verb main verb have infinitive
past simple I had to work yesterday.
present simple I have to work today.
future simple I will have to work tomorrow.
present continuous She is having to wait.
present perfect We have had to change the time.
modal (may) They may have to do it again.
Must (subjective obligation)
We often use must to say that something is essential or necessary, for example:
• I must go.
Structure of Must
Must is a modal auxiliary verb. It is followed by a main verb. The structure is:
subject + must + main verb
The main verb is the base verb (infinitive without "to").
Look at these examples:
subject auxiliary must main verb
I must go home.
You must visit us.
We must stop now.
Like all auxiliary verbs, must CANNOT be followed by to. So, we say:
• I must go now. (not *I must to go now.)
Use of Must
In general, must expresses personal obligation. Must expresses what the speaker thinks is necessary. Must is subjective. Look at these examples:
• I must stop smoking.
• You must visit us soon.
• He must work harder.
In each of the above cases, the "obligation" is the opinion or idea of the person speaking. In fact, it is not a real obligation. It is not imposed from outside.
It is sometimes possible to use must for real obligation, for example a rule or a law. But generally we use have to for this.
We can use must to talk about the present or the future. Look at these examples:
• I must go now. (present)
• I must call my mother tomorrow. (future)
We cannot use must to talk about the past. We use have to to talk about the past.
Must not/Mustn't (prohibition) »
Must not, Mustn't (prohibition)
We use must not to say that something is not permitted or allowed, for example:
• Passengers must not talk to the driver.
Structure of Must not
Must is an auxiliary verb. It is followed by a main verb. The structure for must not is:
subject + must not + main verb
The main verb is the base verb (infinitive without "to").
Must not is often contracted to mustn't.
Look at these examples:
Subject auxiliary must + not main verb
I mustn't forget my keys.
You mustn't disturb him.
Students must not be late.
NB: like all auxiliary verbs, must CANNOT be followed by "to". So, we say:
• You mustn't arrive late. (not You mustn't to arrive late.)
Use of Must not
Must not expresses prohibition - something that is not permitted, not allowed. The prohibition can be subjective (the speaker's opinion) or objective (a real law or rule). Look at these examples:
• I mustn't eat so much sugar. (subjective)
• You mustn't watch so much television. (subjective)
• Students must not leave bicycles here. (objective)
• Policemen must not drink on duty. (objective)
We can use must not to talk about the present or the future:
• Visitors must not smoke. (present)
• I mustn't forget Tara's birthday. (future)
We cannot use must not to talk about the past. We use other structures to talk about the past, for example:
• We were not allowed to enter.
• I couldn't park outside the shop.
Now check your understanding »
I. Have to, Must, Must not Quiz
1 Yesterday I________ finish my Geography project.
2 She will_________ wait in line like everyone else.
3 All employees ________ on time for work.
4 We________ forget to take the chicken out of the freezer.
5 If you are under 13 you ___________ to get your parents' permission.
6 Your daughter may___________ try on a few different sizes.
7 The doctor__________ get here as soon as he can.
8 Do you____________ work next weekend?
9 Bicyclists__________ remember to signal when they turn.
10 Angela, you ___________ leave your clothes all over the floor like this.
II. EXERCISE 1. Fill in the blanks with MUST / MUSTN’T / HAVE TO / NOT HAVE TO
1. Ronaldo can go to Brazil next week because he ________________ attend the training.
2. You ______________ buy that CD. We have got so many Cds at home.
3. Look at my car. It’s really dirty. I ____________ wash it as soon as possible.
4. I have just ordered some pizza. You ____________ cook anything tonight.
5. Since Alex de Souza was injured in the middle of the match, he ___________ leave the pitch.
6. You ___________ remember what I said to you. It’s very important.
7. You ___________ put the chains on the wheels. It’s going to be snowy.
8. Tayfun ___________ buy a new CD player. He can use mine.
9. In Turkey all men _____________ do military service.
10. You __________ prepare an impressive CV before applying a job.
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