verb (3rd singular present and past ought)[with infinitive]
Old English āhte, past tense of āgan 'owe' (see owe)
The verb ought is a modal verb and this means that, grammatically, it does not behave like ordinary verbs. In particular, the negative is formed with the word not alone and not also with auxiliary verbs such as do or have. Thus the standard construction for the negative is he ought not to have gone. The alternative forms he didn’t ought to have gone and he hadn’t ought to have gone, formed as if ought were an ordinary verb rather than a modal verb, are found in dialect from the 19th century but are not acceptable in standard modern English.
A modal auxiliary verb used to refer to possible, rather than actual, events. It expresses a view about how desirable an action might be and is normally followed by the infinitive of the main verb:You ought to go and see a doctor. It can also stand alone:No, I ought not. NegativeThe negative form of verb phrases containing ought is formed simply by adding not: you ought not to go and see the doctor. It is not standard English to use didn't ought to.