This paper deals with the following issues : – Properties of classical negation; – 1. Negation from an algebraic viewpoint; – 2. From bivalence to many-valuation (Gappy logics; Glutty logics); – 3. From many-valuation to bivaluation (Gappy logics; Glutty logics); – 4. Conclusion : Negation as dichotomy (Dichotomy and n-chotomies; Negations as specific functions).