When it is necessary or obligatory to do something, you express obligation.
Obligation in the present
- I have to finish my work before this evening.
- I have got to learn English if I want to live in the USA.
- I must see the doctor soon because I don’t feel well.
- It is obligatory that I stop when the traffic light turn red.
- It is necessary that I take a taxi. I’m late.
Obligation in the past
- I had to work extra hours to pay my bills.
Obligation in the future
- I‘ll have to borrow money.
Things to remember
- The difference between “Have to” and “must” is that “have to” indicates that someone else has imposed conditions on us.
- The simple past of “must” is “had to“.
- The simple future of “must” is “will have to“.
- Should also expresses obligation. But there is a difference between must / have to and should:
- must / have to = 100% obligation.
- “When the traffic light turn red, you must stop.”
- should = 50% obligation. It’s more an advice than an obligation.
- “You look tired. You should have a rest.”
Dialogue
| Policeman: | Don’t you know that you must stop when the traffic lights are red? |
| Driver: | Sorry sir. I was so absent-minded that I didn’t pay attention to the traffic lights. |
| Policeman: | Well sir, you‘ll have to pay a fine! |
