Rhetoric - "speaking" - originally the science of public speaking, then sometimes widely understood as the theory of prose, or the theory of argumentation in general.
Classical Rhetoric
Its top European rhetoric gets in ancient Greece, the Sophists in the schools, the main task of which was a purely practical training eloquence, and so their rhetoric is concluded many rules pertaining to the proper style and grammar.
Major theorists: Aristotle, Cicero, Kvintilian.