Modals to express obligation: MUST, HAVE (GOT) TO
Present and future
Must refers to obligations which come from the speaker and may be directed at the speaker or the listener:
I really must give up smoking. (directed at the speaker)
You must keep this secret. (directed at the listener)
Have to expresses external obligations, which come from outside of the speaker. These may be rules and regulations imposed by an external authority:
I have to get to work by 9 every day.
Do you have to wear a uniform at your school?
Absence of obligation is expressed with the negative form of have to, not with mustn't. Mustn't is used to express that it is necessary not to do something:
I don't have to get up early tomorrow. It's a holiday. (I can get up late.)
You mustn't tell anyone. It's a secret. (Don't tell anyone.)
Have got to has the same meaning as have to, but it is more common in informal, spoken language. The affirmative, negative and interrogative forms of have to and have got to are:
| have to | have got to |
|---|---|
| I/you/we/they have to go. I/you/we/they don't have to go. Do I/you/we/they have to go? He has to go. He doesn't have to go. Does he have to go? |
I/you/we/they have got to go. I/you/we/they haven't got to go. Have I/you/we/they got to go? He has got to go. He hasn't got to go. Has he got to go? |
Must and will have to can be used to refer to future obligations:
You must be home by 10 o'clock.
I'll have to pay my bills next week.
Past
Must has no past form. Instead, we use had to to express past obligations:
When I was at primary school, I had to wear a uniform.
We had to start all over again.
