Based on an idea ofAjdukiewiu, a method of equifunctionalityis developed to provide a formal explication of the notion of sameness of use relative to some system of rules. Given this, a set‐theoretic explication of Lauener's context dependent conception ofsynonymyis introduced by looking at languages of ropositional logic, and compared both with Ajdukiewicz's original conception and with Carnap's explication of synonymy based on hismethod of extension and intentio