Uses of Must and Ought (to)
Compare:
- He must go home. (Future / present)
- He must have gone home. (Past)
- We must see the minister now. (Present)
- He must have seen the minister by now. (Past)
- You must file a writ petition. (Future)
Must expresses compulsion or strong obligation. It is much stronger than should.
- He must apologize for his mistakes.
- They must pay the fine.
- You must be loyal to your country.
- We must get up early and start on our way.
- Must we wait for them?
Must can express probability or likelihood.
- He must be mad to do this.
- Oh, there is the door bell; that must be the postman.
Must signifies strong determination.
- I must have my own way.
Ought is different from other modal auxiliary verbs; it is followed by an infinitive with to.
Compare:
- I ought to go.
- I must go.
- She must wait.
- She ought to wait.
- We ought to help the poor and the needy. (Duty)
- You ought to exercise regularly. (Necessity)
- She ought to be back by 10 o’clock.
- You ought to have helped him.