NotD

notD is an informal, multi-domain term used to denote the negation or complement of a concept labeled D. Because D can represent a proposition, a set, a condition, or a boolean variable, notD inherits different formal meanings depending on context.

In logic and set theory, notD often corresponds to the negation of D, written as ¬D or not D, or to the complement of a subset D within a universal set U, sometimes denoted D^c. In probability and statistics, notD is used to denote the event that D does not occur, with P(notD) = 1 − P(D) for a dichotomous outcome.

In computing and programming, notD may appear as a negated boolean expression formed by the logical not operator, for example if notD: ...; in many languages, a variable named notD can hold a boolean value representing the failure of D. The exact behavior is language- and domain-dependent.

NotD does not have a single canonical definition; it is a flexible shorthand that relies on the surrounding notation to convey its precise meaning.

See also negation; complement; not operator.