The overall aim of this article is to argue that the functioning of every language system is based on a potential multilingual competence. The empirical basis for this is now broad enough to gain a comprehensive view on the overall competence of a multilingual individual. Moreover, increasing theoretical reflection has conferred an increasingly independent profile in the field of multilingualism research. In the main part of this article, a definition of multilingualism is proposed and related to the term "multicompetence." The proposed definition of multilingualism, emerging from sociolinguistically rooted studies, distinguishes not only the classical social, institutional, and individual dimensions of observation but includes a new interaction dimension as well. The term "multicompetence" is then discussed in its historical development form on which psycholinguistics oriented studies. The European LINEE project tries to enlarge the concept of multicompetence with the aim of making it suitable for a sociolinguistic embedding. This usage-based approach is presented and further claims for more conceptual reflections in the field of multilingualism are made.