Specialized communication is a central subject of applied linguistics and language didactics. However, research and development in this area has so far lacked a conceptual basis for adequately assessing and relating empirical or didactic studies to one another. This monograph now provides such a basis. On the one hand, it includes a general model of specialized communication as well as three concepts of research into Languages for Specific Purposes. On the other hand, models of subject specialization, communicative efficiency and professional diversity are presented and linked to the general model of specialized communication. Finally, these models are discussed using a number of examples.