/ ˈɔːt tə; NAmE ; before vowels and finally ˈɔːt tu/ modal verb ( negative ought not to , short form especially BrE oughtn't to )
1.
used to say what is the right thing to do :
They ought to apologize.
'Ought I to write to say thank you?' 'Yes, I think you ought (to).'
They ought to have apologized (= but they didn't) .
Such things ought not to be allowed.
He oughtn't to have been driving so fast.
➡ note at should
2.
used to say what you expect or would like to happen :
Children ought to be able to read by the age of 7.
Nurses ought to earn more.
3.
used to say what you advise or recommend :
We ought to be leaving now.
This is delicious. You ought to try some.
You ought to have come to the meeting. It was interesting.
4.
used to say what has probably happened or is probably true :
If he started out at nine, he ought to be here by now.
That ought to be enough food for the four of us.
Oughtn't the water to have boiled by now?
➡ note at modal