Must and Have to

'Have to' and 'must' have the same meaning and are used to express obligations. However, they are used in different situations and are not interchangeable.

Must and Have to in English Grammar

Must and Have to

In this lesson, we will study two modal verbs: Must and Have to.
'Must' and 'have to' are used in the present to say that something is necessary or should be done. Have to is more common in American English.

Must

'Must' is a modal verb and it has different uses in English. It is used to talk about:

  1. expressing rules or laws
  2. expressing something likely or logical
  3. making suggestions and recommendations

Expressing Rules or Laws

'Must' can be used to express something necessary or very important like a rule or a law.

All applicants must submit their resumes.

You must be home by 11 o’clock.

In this case we are not referring to a law, but it is actually the rule of our house.

Expressing Something Likely or Logical

'Must' is used to say that something is likely or logical.

You must be hungry after walking for a long time.

obviously, It is logical to get hungry after long hours of walk.

If you are talking about the past, use 'must have' + 'past participle'

He must have known what she wanted.

Making Suggestions and Recommendations

'Must' can also be used to recommend that somebody do something because you think it is a good idea. This use is more common in British English.

You simply must watch this movie.

We must get together for lunch.

Have to

'Have to' or 'have got to' is a modal verb and it is used to talk about:

  1. necessity and obligation
  2. giving advice or recommendation
  3. certainty
  4. an annoying event

Necessity and Obligation

'Have to' or 'have got to' is used to show that you must do something.

Sorry, I've got to go.

In this example the person is actually saying that they must go.

You 'have to' think about the consequences of your actions.

Must, Have to and Have Got to

Must and have (got) to are synonymous in this use, i.e. expressing obligation and necessities.
In British English there is a difference between them. 'Must' is used to talk about what the speaker or listener wants, and have (got) to about other people’s wishes, rules or laws.

You must apply for a visa.

You have to apply for a visa.

Past Obligations or Necessities

'Must' does not have a past form. To talk about the past, you use 'had to' or 'to have had to'.

I __had to wait__ an hour for the train.

Sara __has had to study__ a lot for her English exam.

Future Obligations or Necessities

'Must' does not have a future form. To talk about the future you use 'will have to' or 'have to' if an arrangement has already been made.

She'll have to hurry up, if she wants to arrive on time.

I have to go to the dentist tomorrow.

Giving Advice or Recommendation

'Have to' in American English or 'have got to' in British English is used to give advice or recommend something.

You simply have to tell him the truth.

In this case the person is giving a piece of advice.

You've got to try this snack—it's delicious.

As you can imply from the meaning; the person is not giving advice, they are recommending.

Questions

As mentioned, modals do not need an auxiliary verb for questions or negation. But 'have to' is different. Questions with 'have to' are formed using the auxiliary verb 'do'.

Do we have to pay the fee beforehand?

You don't have to wear a uniform.

Negations

In negative sentences both 'must not' and 'don’t/doesn't have to' are used, but with different meanings. 'Must not' is used to tell somebody not to do something.

You must not make a noise in this room.

You mustn't leave the window open.

'Don't/doesn't have to' is used when it is not necessary to do something.

We don't have to work at weekends.

Here, the person tells they are not forced to work at weekends.

Certainty

'Have to' is used to express something that must be true.
Both 'must' and 'have to' are used to say that you are certain about something. 'Have to' is more common in American English.

There has to be a reason for his strange behavior.

Here, the person is in fact declares that he is sure.

If you want to talk about the past, use 'must have' + 'past participle'.

Your trip must have been fun!

Annoying Events

'Have to' is used to express an annoying event that you think happens in order to annoy you, or that somebody does something in order to annoy you.

Just our luck. It had to start raining as soon as we got to the beach.

'It had to start raining' bears an annoying concept.

Does he have to speak so loudly on the phone?

It is implied that 'Speaking loudly on the phone' annoys the speaker.

Review

'Have to' and 'must' are used to express obligations. They have many other functions. We can learn them sooner by examples.

must
expressing rules or laws You must speak to the secretary first.
expressing something likely or logical He must be sleeping now, he works 18 hours per day.
making suggestions and recommendations You must try the turkey sandwich.
Have to
necessity and obligation You have to pay your own bills.
giving advice or recommendation They have to be patient to get the job.
certainty It has to be Mark. I remember he had these ocean blue eyes when he was younger.
an annoying event I wonder why it has to always be me who is in charge of everything.

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