Must vs. Should
Must (NECESSARY)
modal verb
1 used to show that it is necessary or very important that something happens in the present or future:
Meat must be cooked thoroughly.
I must get some sleep.
You mustn't show this letter to anyone else.
Luggage must not be left unattended (= it is against the rules).
FORMAL Must you leave so soon?
FORMAL "Must I sign this?" "No, there's no need."
Must(PROBABLY)
modal verb
used to show that something is very likely, probable or certain to be true:
Harry's been driving all day - he must be tired.
There's no food left - we must have eaten it all.
When you got lost in the forest you must have been very frightened.
"You must know Frank." "No, I don't."
Should (DUTY)
modal verb
used to say or ask what is the correct or best thing to do:
If you're annoyed with him, you should tell him.
You should change trains at Peterborough if you're going to Newcastle.
"Should I apologize to him?" "Yes, I think you should."
You should be ashamed of yourselves.
This computer isn't working as it should.
There should be an investigation into the cause of the disaster.
Should (PROBABLE)
modal verb
used to show when something is likely or expected:
My dry cleaning should be ready this afternoon.
You should find this guidebook helpful.
modal verb
1 used to show that it is necessary or very important that something happens in the present or future:
Meat must be cooked thoroughly.
I must get some sleep.
You mustn't show this letter to anyone else.
Luggage must not be left unattended (= it is against the rules).
FORMAL Must you leave so soon?
FORMAL "Must I sign this?" "No, there's no need."
Must(PROBABLY)
modal verb
used to show that something is very likely, probable or certain to be true:
Harry's been driving all day - he must be tired.
There's no food left - we must have eaten it all.
When you got lost in the forest you must have been very frightened.
"You must know Frank." "No, I don't."
Should (DUTY)
modal verb
used to say or ask what is the correct or best thing to do:
If you're annoyed with him, you should tell him.
You should change trains at Peterborough if you're going to Newcastle.
"Should I apologize to him?" "Yes, I think you should."
You should be ashamed of yourselves.
This computer isn't working as it should.
There should be an investigation into the cause of the disaster.
Should (PROBABLE)
modal verb
used to show when something is likely or expected:
My dry cleaning should be ready this afternoon.
You should find this guidebook helpful.