* You use `should’ and `ought’ to talk about mild obligation.
* You use `should have’ and `ought to have’ to say that there was a mild obligation to do something in the past, but it was not done.
* You can also use `had better’ to talk about mild obligation.
1 You can use `should’ and `ought’ to talk about a mild obligation to do something. When you use `should’ and `ought’, you are saying that the feeling of obligation is not as strong as when you use `must’.
`Should’ and `ought’ are very common in spoken English.
`Should’ is followed by the base form of a verb, but `ought’ is followed by a `to’-infinitive.
When you want to say that there is a mild obligation not to do something, you use `should not’, `shouldn’t, `ought not’, or `oughtn’t’.
2 You use `should’ and `ought’ in three main ways:
* when you are talking about what is a good thing to do, or the right thing to do.
We should send her a postcard.
We shouldn’t spend all the money.
He ought to come more often.
You ought not to see him again.
* when you are trying to advise someone about what to do or what not to do.
You should claim your pension 3-4 months before you retire.
You shouldn’t use a detergent.
You ought to get a new TV.
You oughtn’t to marry him.
* when you are giving or asking for an opinion about a situation. You often use `I think’, `I don’t think’, or `Do you think’ to start the sentence.
I think that we should be paid more.
I don’t think we ought to grumble.
Do you think he ought not to go?
What do you think we should do?
3 You use `should have’ or `ought to have’ and a past participle to say that there was a mild obligation to do something in the past, but that it was not done. For example, if you say `I should have given him the money yesterday’, you mean that you had a mild obligation to give him the money yesterday, but you did not give it to him.
I should have finished my drink and gone home.
You should have realised that he was joking.
We ought to have stayed in tonight.
They ought to have taken a taxi.
You use `should not have’ or `ought not to have’ and a past participle to say that it was important not to do something in the past, but that it was done. For example, if you say `I should not have left the door open’, you mean that it was important that you did not leave the door open, but you did leave it open.
I should not have said that.
You shouldn’t have given him the money.
They ought not to have told him.
She oughtn’t to have sold the ring.
4 You use `had better’ followed by a base form to indicate mild obligation to do something in a particular situation. You also use `had better’ when giving advice or when giving your opinion about something. The negative is `had better not’.
I think I had better show this to you now.
You’d better go tomorrow.
I’d better not look at this.
WARNING: The correct form is always `had better’ (not `have better’). You do not use `had better’ to talk about mild obligation in the past, even though it looks like a past form.