Must & Have To

                                                  HAVE TO

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 basic structure for have to is:

subject + auxiliary verb + have + to-infinitive


Look at these examples in the Present Simple tense:

subject auxiliary verb main verb
+ 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 tois 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 comes 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
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.




We often use must to say that something is essential or necessary, for example:

  • must go.


Structure of must:

Must is a modal auxiliary verb. It is followed by a main verb.


The basic structure for must is:

subject + auxiliary verb
+ main verb


The main verb is always the same form: base

Look at these examples:

subject auxiliary verb
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:

  • 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:

  • must go now. (present)
  • must call my mother tomorrow. (future)

We cannot use must to talk about the past. We use have to to talk about the past.





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