This paper presents the historical background and practical applications of "Interlingua," a language system of common words derived from four control languages. Interlingua and "Esperanto," another artificial language, are compared, emphasizing that international, cross-cultural communication is best served, not by the institution of a universal language, but by the formulation of an auxiliary language that is internationally understood. The paper also stresses that the development of auxiliary language entails linguistic sensitivity and native-language appreciation. (RL)