Ought

Ought (/ɔ:t/) is an English semi-modal verb.

In standard English it is generally treated as a full modal verb, lacking an infinitive, present participle and past participle, with the exception that it catenates with a to-infinitive rather than a bare infinitive: The question tag form is without to; e.g. "ought you?" or "oughtn’t you?.”

It basically means should. Ought to is a little more formal than should - but using it instead of should adds a word (see word count). For past time, it can take the perfect.

However in non-standard English the "to" can be dropped.

Type	Simple	Perfect
Positive	You ought to do something	You ought to have done something
Negative	You ought not to do something You oughtn’t to do something	You ought not to have done something You oughtn’t to have done something You ought to have not done something
Question	Ought you to do something?	Ought you to have done something?
Negative question	Oughtn’t you do something?	Oughtn’t you have done something?