Abstract
The work presented here focuses on the semiolinguistic dimension of elementary algebra knowledge (Drouhard, 2012) and on a particular object of knowledge: substitution. Analyses of textbooks and teaching practices (Constantin, 2014, 2018) have led us to postulate that this knowledge is part of what Margolinas and Laparra (2011) call transparent knowledge for the teacher. From an ecological questioning (Artaud, 1997), we seek to determine the conditions, constraints, but also the potentialities to consider such an object of knowledge for the teaching of elementary algebra. To do this, we rely on a double epistemological and didactic analysis before addressing the results of an experiment conducted in a middle school class.