discusses the role of language in teaching and in communication of scientific and technical subjects. It identifies and analyzes the many strategies teachers and students use to communicate about science and to influence one another's beliefs and behavior. Special emphasis is placed on analyzing patterns of social interaction, the role of language and semantics in communicating scientific concepts, and the social values and interests which lie behind these patterns of communication. Working from transcripts of recordings made in real science classrooms, this volume goes beyond previous work on the organization of classroom discourse to show how the conceptual content of a specialized subject is actually communicated through the semantic patterns that teachers and students weave with language. Modern techniques of discourse analysis are used to place the communication of science in the context of classroom lessons, debates, and disruptions. Critical analysis further shows how a mystique of science is perpetuated in classrooms and identifies the hidden social interests it serves.