Must and Have to for Obligation
If an action is necessary (obliged to) to be done, we use have to.
- You have to do your homework if you want to pass your exam.
- You have to turn right, not left.
- You have to wear your glasses to read clearly.
- I can’t go to the party with you tonight. I have to work hard for my post-graduate degree.
- Last month, Luis broke her leg so that she had to go to the hospital.
For making questions:
- Do you have to wait here for a long time?
- Why did you have to work hard?
For negative sentences:
- No, I don’t (No, I don’t have to wait…)
- Yes, I had to.
- No, I didn’t have to.
For future situations:
- I will have to buy a new iPad next term.
- I am going to have to study late tonight.
Must and Have to
Must is used when expressing personal opinions or giving advice, while have to is used for formal rules and instructions.
- It is too late. I have to go / I must go.
- I must assess her homework by tomorrow / I have to assess… .
- I met a really nice friend yesterday. You must meet him, too / You have to meet him…
Mustn’t and Don’t Have To
The negative forms of “must” and “have to” have different meanings.
- You mustn’t be late for the club meeting. Everybody is obliged to join.
- You don’t have to be late (you don’t need to be late).
- You don’t have to tell anyone (it’s optional to tell).
Additionally, “have got to” can be used instead of “have to”.
- He gets up at 7 every day.
- There was nobody around. I had to carry it by myself.
- I broke my leg. I had to go to the hospital.
- We don’t have much time. We have to go.
- What time do you have to go?