Negation in Moroccan Arabic is marked either by the single element ma- or by the association of ma- with the element -š or its variant -ši. The description of the complex relationships between these two elements requires taking into account different levels of analysis: morphology, syntax, semantics, lexicology, pragmatics, but also logic. This paper is aimed to understanding the use of negation in synchrony in Moroccan Arabic. In particular, it defends the hypothesis that ma- should necessarily be correlated with an [+undefined] quantifier. The association with -š is linked to the presence or absence of this feature, but also to the pragmatic force of negation.