The main aim of this paper is to develop, from an analytical viewpoint, the sociological notion of social convention. To this end, the article takes as a starting point the classic notion of convention proposed by Max Weber. Then the normative character of conventions is studied in depth, defining a convention as a tacit and jointly accepted principle of action. Such a principle is supported by mechanisms of approval and disapproval that define the actions as appropriate or inappropriate, in relation to the prescribed principle. Furthermore, the analytical distinction between social conventions and moral norms is stated.