Academic discourse (the language, organization, and rhetoric of academic texts) is a member of a set of discourses called “language for specific purposes” (LSP), which include business, legal, and technical discourse. These discourses occur in spoken and written texts of many sorts. Their vocabulary and grammar can be called their registers, so that one could speak of a general academic written register characterized, for example, by formality and precision, and, within that, of the register of chemistry, characterized above all by a particular terminology. But all these LSP discourses are also characterized by having a particular set of genres (i.e., types of texts with a particular purpose and audience, for example textbooks, research articles, student essays). They use the grammar of the general language but the frequency and functions of some features are different, depending partly on the genre.