Unit 27. must
|must + infinitive (must do / must see etc.):
Use must when you think it is necessary or very important to do something:
- The windows are very dirty. I must clean them.
- It's a fantastic film. You must see it.
- We must go to the bank today. We haven't got any money.
must is present or future:
- I must go to the bank now.
- I must go to the bank tomorrow.
For the past (yesterday / last week etc.), we use had to + infinitive (had to go / had to do / had to write etc.):
- I had to go to the bank yesterday. (= It was necessary for me to go to the bank.)
- We had to walk home last night. There was no bus.
See Unit 29 have to …
mustn't (must not)
|I mustn't do it = it is important not to do it, it is a bad thing to do:
- I must hurry. I mustn't be late.
- I mustn't forget to phone George. (=1 must remember)
- You mustn't walk on the grass. (= Don't walk on the grass.)
needn't (need not)
I needn't do it = it is not necessary to do it, I don't need to do it:
- I needn't clean the windows. They aren't dirty.
- You needn't go to the bank. I can give you some money.
You can also say don't need to … (= needn't):
- I don't need to clean the windows.
- You don't need to go to the bank.