The unit kan 'be' in Moroccan Arabic (MA) is traditionally identified as a copula in the context of a non verbal unit and as an auxiliary in the context of a verbal unit. We argue here that the notion of copula, borrowed from the Indo-European languages, is not relevant for kan in MA. Kan is not a copula but a connective verb. Although it is semantically weak, kan is syntactically a full verb, particularly a bivalent verb requiring two essential arguments: a subject and an attribute. Therefore, in the connective structures, kan is the syntactic nucleus (syntactic predicate). Moreover we show that kan, in the context of a verbal unit, even though it exhibits some auxiliarity's features - is not an auxiliary inasmuch as it doesn't form a "structure of auxiliarity" (Simeone-Senelle & Vanhove 1997: 86) - i.e. a morphological, semantic and syntactic unit - with a second verb. Kan is a bivalent existence-verb governing two arguments; the second argument can be a verbal phrase.