This paper is devoted to the effect of negative polarity on presuppositions and scalar implicatures, negative quantifiers and negative events. The main thesis is that the semantics of negation, depending on its scope, do not cover all the properties and relations of the sentence meaning. When ordinary negation is used, it does not touch the presupposition whereas when negation is metalinguistics, it either asserts or negates the proposition, and either asserts or negates its implication. When negation is used with a negative particular (down-bounded quantifier), it preserves its negative scalar up-bounded implicature. Finally, when used with an event, negation preserves the relational domain of the semantics of event, i.e. its temporal (directional) inference. These properties of negation contrast with the complement function of logical negation.