In this article, the concept of competence is studied from the point of view of the semiotics of education. It will be claimed that it is a central key concept when we are trying to analyse the meaning of education. Educational action can be reasonably understood as an insecure and complicatedly mediated trial to affect another person's competence. First, the recent discussion about the concept of competence and its relatives is shortly reviewed. Then, competence is analysed and defined according to Greimassian semiotic theory as a basic determining character of an acting subject. At the same time as competence is indispensably central for understanding the subjects of action, it is problematically empirically ineffable. This ineffability has a special meaning in education, where we must try to both plan our own educative action and evaluate the learning of the student according to these invisible features. It is proposed that in the recent discourse of education, the very popular use of the concept of competence is misguided and problematically mixed with its conceptual counterpart performance. From this viewpoint, the concept of competence should rather be connected to the ontological concept of disposition. The problem of multi-dimensionality of competence is considered with the help of the Greimassian conception of modalities to create a richer and more detailed picture of the role of competence in action, and especially in education.