Unit 33: MUST AND SHOULD
Must and should are modal verbs. Unit 27 shows you how to make correct sentences with them. This unit shows you when to use them. They have the same kinds of meaning, but must is always stronger than should.
Commands (must only)
You must not leave the room until I say.
Parking permits must be displayed in car windows.
Advice or necessity
EXAMPLE: You shouldn't ever cross the road without looking.
PRESENT AND FUTURE TIME
Do you think we should take our coats?
Yes, you must; it might be very cold.
I'm afraid we really must go now.
PAST TIME (SHOULD ONLY)
You shouldn't have been rude. It was bad of you.
They should have told him. Why didn't they?
GENERAL (MUST or have got to)
It must be terrible to be in an earthquake.
It has got to be terrible to be in an earthquake.
(I have not been in one but I feel sure.)
This isn't my bill. There must be some mistake.
This isn't my bill. There has got to be some mistake
(I am sure there is a mistake.)
(I can't believe it.)
He should be in his office.
(He is probably there.)
Don't worry. You shouldn't have any problems.
(I don't think you will have problems.)
PAST TIME (MUST ONLY)
I can't see them anywhere. They must have gone home.
(I feel sure that they have gone home.)
I saw them just now. They can't have gone home.
(I feel sure they have not gone home.)
For strong negative probability, use can't (Unit 28).
NOTICE: Ought to (Unit 36) means the same as should.