The study of mental representations was so important in the past, that it occulted the need for studying the semiotic representations from this perspective as well as the construction of concepts from that of problem solving. The study of the semiotic representations has allowed us a new approach on the construction of mathematical concepts. However, in our opinion, after the major importance given to the study of mental representations, another extreme consists in considering only the study of the role of semiotic representations. We need a balance in order to get satisfactory explanations on general processes of learning and on particular construction of mathematical concepts. In this article, we want to stress the functional character of the representations and especially to understand their role in the process of learning. So we focus our attention to the whole of the semiotic representations produced by an individual in situation of construction of a concept or in a problem solving situation.