ABSTRACT
This chapter provides 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 many parts of the world a trade language serves the purpose of out-group communication. In the lower Congo and the Kwilu valley a trade language called Kituba serves for most intertribal contacts. Linguists have generally assumed that any language is adequate for communicating any and all ideas that the members of its speech community have occasion to deal with—granting, of course, that new terms may need to be borrowed or new expressions coined with the intrusion of new ideas.
