The prose is a form of written (or spoken) language that usually exhibits a natural flow of speech and grammatical structure - an exception is the narrative device stream of consciousness.

English Grammar Terms II

In linguistics, the grammar of a natural language is its set of structural constraints on speakers 'or writers' composition of clauses, phrases, and words. The term can also refer to the study of such constraints, a field that includes domains such as phonology, morphology, and syntax, often complemented by phonetics, semantics, and pragmatics. There are currently two different approaches to the study of grammar, traditional grammar and theoretical grammar.