As a variable grammatical class, the adjective is a fundamental notion of school grammar, its noun dependence and the morphological marking of this relation being the pillars of its definition. However, recent research results invite us to weight the evidence of the linguistic concept. Thus, this article first attempts to put the relevant reference knowledge into perspective, by considering different constructions in which the concept appears. Once this framework established, we provide an overview of what research tells us about pupils’ knowledge of the adjective, before evaluating how they are the product of a certain didactic transposition, which we believe necessary to question.