A REGISTER is a variety of English, such as conversation, newspaper language, fiction, academic prose.
A TEXT is an extended sample of language from a register. It may be written (like a history textbook, a novel or a newspaper report) or spoken (a face-to-face conversation or a lecture).
A DISCOURSE is the set of all the factors that influence the interpretation of the instance of language in actual use. Here belong linguistic, situational, social, psychological and pragmatic factors.
A CORPUS (plural corpora) is a large and structured set of texts, usually stored and processed electronically, used to do research like statistical analysis or validating linguistic rules within a specific language territory.
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