As a generalization of fuzzy negation, the one’s complement is most commonly used (in applications almost exclusively)
NOT a = 1 – a
Other works mention, for example, Sugeno class of complements
NOTλ a = (1 - a)/(1 - λa) for the parameter λ in the interval (-1, ∞)
or Yager class of negations
NOTw a = (1 - aw)1/w