Description is one of four rhetorical modes (also known as modes of discourse), along with exposition, argumentation, and narration. Each of the rhetorical modes is present in a variety of forms and each has its own purpose and conventions. The act of description may be related to that of definition. Description is also the fiction-writing mode for transmitting a mental image of the particulars of a story. Definition: The pattern of development that presents a word picture of a thing, a person, a situation, or a series of events.