Frequency: The word is one of the 3000 most common words in English.
Note: 'Ought to' is a phrasal modal verb. It is used with the base form of a verb. The negative form of '~ to' is '~ not to', which is sometimes shortened to '~n’t to' in spoken English.
1.
You use ~ to to mean that it is morally right to do a particular thing or that it is morally right for a particular situation to exist, especially when giving or asking for advice or opinions.
Mark, you’ve got a good wife. You ~ to take care of her...
You ~ to be ashamed of yourselves. You’ve created this problem.
= should
PHRASE
2.
You use ~ to when saying that you think it is a good idea and important for you or someone else to do a particular thing, especially when giving or asking for advice or opinions.
You don’t have to be alone with him and I don’t think you ~ to be...
You ~ to ask a lawyer’s advice...
We ~ not to be quarrelling now.
= should
PHRASE
3.
You use ~ to to indicate that you expect something to be true or to happen. You use ~ to have to indicate that you expect something to have happened already.
‘This ~ to be fun,’ he told Alex, eyes gleaming.
= should
PHRASE
4.
You use ~ to to indicate that you think that something should be the case, but might not be.
By rights the Social Democrats ~ to be the favourites in the election. But nothing looks less certain...
Though this gives them a nice feeling, it really ~ to worry them.
= should
PHRASE
5.
You use ~ to to indicate that you think that something has happened because of what you know about the situation, but you are not certain.
He ~ to have reached the house some time ago.
= should
PHRASE vagueness
6.
You use ~ to have with a past participle to indicate that something was expected to happen or be the case, but it did not happen or was not the case.
Basically the system ~ to have worked...
The money to build the power station ~ to have been sufficient.
PHRASE
7.
You use ~ to have with a past participle to indicate that although it was best or correct for someone to do something in the past, they did not actually do it.
I realize I ~ to have told you about it...
Perhaps we ~ to have trusted people more...
I ~ not to have asked you a thing like that. I’m sorry...
I’m beginning to feel now we ~n’t to have let her go away like that.
PHRASE
8.
You use ~ to when politely telling someone that you must do something, for example that you must leave.
I really ~ to be getting back now...
I think I ~ to go.
= should
PHRASE politeness