Most closely associated with the theorist Michel Foucault (1926-1984), discourse most often refers to the groups of statements which form knowledge about a particular subject area, profession, institution, identity, political camp, technical speciality or religion. For example, there are discourses of medicine, film making, cookery, Buddhist philosophy, computing and education. Critical Theory is also a discourse. A discourse can be thought of as the group of acceptable statements which can be made in a particular area or as the set of rules which preside over the statements. Discourses, therefore open a space for certain things to be said while prohibiting others. Crucially for Foucault, discourse is connected with power. Only specific people are given access to each discourse and there are strict limitations on what can be expressed within each discourse. Finally, so long as someone is making sense, they are speaking or writing within a discourse. There is no outside to discourse.

For more detail see The Order of Discourse