The purpose of this paper is to provide a model for studying languages in reference to their communicative functions, especially in multilingual societies; and to point out some of the factors that should be taken into consideration by educators and policy-making bodies who are concerned with the development of national languages and with making optimal use of other languages in their areas. In this approach the paper differs from a number of other studies of the role of language which focus on the function of language within different contexts. 1