not

Not is a negation particle in English used to deny or negate a statement. It typically follows an auxiliary or modal verb, as in It is not possible or They do not know. When the main verb has no auxiliary, modern English uses do-support: I do not believe. Not also modifies adjectives and adverbs, as in not happy or not often, and can appear in fixed expressions such as not only or not yet.

In syntax, the scope of not applies to the verb phrase or to the word it directly negates. The use of not interacts with auxiliary verbs and sometimes alters word order in questions or emphasis. Double negation of standard usage is usually considered nonstandard in formal writing, though it remains common in various dialects and informal speech for emphasis.

Not has a long history as a core negator in Germanic languages. In English, it has cognates in related languages, such as Dutch niet and German nicht, reflecting a shared development of negation across the family. The exact historical forms and their evolution are complex, but not remains a primary means of negation in modern English.

Beyond everyday language, not functions as a logical and computational operator. In formal logic, not (often written as ¬) inverts the truth value of a proposition. In programming, a boolean NOT operation inverts a true value to false and vice versa; different languages use different syntax (for example, not in Python, ! in C-based languages, and NOT in some database query languages).