Definition from Wiktionary, the free dictionary
Contraction of not
- Negates the meaning of the clause in which it occurs.
- The suffix -n’t can only be added to auxiliary verbs, including dare and need in certain uses, and be in almost all uses. Indeed, in some dialects, not even all auxiliary verbs accept -n’t; for example, mayn’t is present in some dialects and absent in others.
- Some verbs change their form when -n’t is added; for example, shall + -n’t is usually shan’t, and am + -n’t is frequently aren’t or ain’t (though all three of these are dialect-dependent).
- Though verbs with -n’t are usually considered contractions of versions using the adverb not, grammatically they behave a bit differently. For example, when subject and verb are inverted, -n’t remains attached to the verb, whereas not does not:
- Isn’t that difficult?
- Is that not difficult?
- Semantically, -n’t may have either “high attachment” or “low attachment”, depending primarily on the verb. For example, “I can’t leave” means “It is not the case that I can leave” (usually “I am unable to leave”), whereas “I shouldn’t leave” means basically “I should stay” (which is a narrower statement, and therefore a stronger one, than “It is not the case that I should leave”). (“I can stay”, by contrast, is very different from “I can’t leave.”) Similar variation is seen with the adverb not, as well as various other negative constructions.