A. You should do something = it is a good thing to do or the right thing to do.
You can use should to give advice or to give an opinion:
* You look tired. You should go to bed.
* The government should do more to help homeless people.
* 'Should we invite Susan to the party?' 'Yes, I think we should.'
We often use should with I think/I don't think/Do you think...?:
* I think the government should do more to help homeless people.
* I don't think you should work so hard.
* 'Do you think I should apply for this job?' 'Yes, I think you should.'
'You shouldn't do something' = it isn't a good thing to do:
* You shouldn't believe everything you read in the newspapers.
Should is not as strong as must:
* You should apologise. (= it would be a good thing to do)
* You must apologise. (= you have no alternative)
B. We also use should when something is not right or what we expect. For
example:
* I wonder where Liz is. She should be here by now. (= she isn't here yet, and this
is not normal)
* The price on this packet is wrong. It should be L1.20, not L1.50.
* Those boys shouldn't be playing football at this time. They should be at school.
We use should to say that we expect something to happen:
* She's been studying hard for the exam, so she should pass. (= I expect her to
pass)
* There are plenty of hotels in the town. It shouldn't be difficult to find somewhere
to stay. (= I don't expect that it will be difficult)
C. 'You should have done something' = you didn't do it but it would have been the
right thing to do:
* It was a great party last night. You should have come. Why didn't you? (= you
didn't come but it would have been good to come)
* I'm feeling sick. I shouldn't have eaten so much chocolate. (= I ate too much
chocolate)
* I wonder why they're so late. They should have been here an hour ago.
* She shouldn't have been listening to our conversation. It was private.
Compare should (do) and should have (done):
* You look tired. You should go to bed now.
* You went to bed very late last night. You should have gone to bed earlier.
D. Ought to ...
You can use ought to instead of should in the sentences on this page. Note that we say 'ought to do...' (with to):
* Do you think I ought to apply for this job? (= Do you think I should apply ...?)
* Jack ought not to go to bed so late. (= Jack shouldn't go ...)
* It was a great party last night. You ought to have come.
* She's been studying hard for the exam, so she ought to pass.
