What is ideal or desired
We use should most commonly to talk about what is the ideal or best thing to do in a situation:
There should be more public hospitals.
They should reduce the price of petrol. It’s so expensive.
There should be four more candles on the cake.
We use should have + -ed form to talk about things that were ideal in the past but which didn’t happen. It can express regret:
Everyone knows that this is a busy restaurant. They should have made a reservation.
I should have studied harder when I was young. I wish I had gone to college.
Advice and suggestions
We often use should to give advice and make suggestions:
You should tell him what you think.
We should leave it until tomorrow; it’s late now.
What is likely to happen
We also use should to talk about what is likely to happen:
Shall we start? Luke’s delayed but he says he should be here in ten minutes.
There should be a very big crowd at the party. Mary has so many friends.
We sometimes use should in hypothetical conditional clauses with if to express possibility. It is formal:
[information leaflet in a hotel room]
If you should wish to use the Internet, there is a code available at the reception desk.
If you should decide not to go on the trip, you will get a full refund.
We can also use Should you as an alternative to If you should in these situations by changing the order of the subject and the verb. Compare these two sentences with the examples above. They have the same meaning and they are also formal:
Should you wish to use the Internet, there is a code available at the reception desk.
Should you decide not to go on the trip, you will get a full refund.
In speaking, we often say you shouldn’t have when someone gives us a gift:
I got you something from Texas. A cowboy hat.B:
Oh Ken, you shouldn’t have!
Surprise or regret
We sometimes use should to express surprise or regret about something that happened:
I’m amazed that he should have done something so stupid.
I’m sorry that he should be so upset by what I said.
Should and would
We use should as a more formal alternative to would with I and we in conditional clauses.
We use should as a more formal alternative to would when we want to be less direct.
Should and ought to
Should and ought to have similar meanings and uses. Ought to is more formal and less common than should:
We should clean up the garden.
We ought to clean up the garden.
Should is much more common in negatives and questions than ought to:
Should we keep a seat for Margaret? (more common than Ought we to keep a seat …?)
He shouldn’t speak to his parents in that way. (more common than He oughtn’t/ought not to speak …)