Discourse studies larger chunks of language as they flow together. It can also be defined as an analysis of speech units larger than the sentence and of their relationship to the contexts in which they are used. Generally, exposition, narration, description, and argumentation are considered to be the basic forms of discourse.When a writer is concerned with setting forth facts then the form is known as exposition, when she/he presents them in terms of temporal action then the form is narration, and in terms of space and giving details about it, it is the description, and when s/he intends to resolve conflict of facts then it is known as argumentation.These forms do not exist as pure forms; they, in fact, are intermixed and one can only talk about a dominant form.Explanatory/Informative/Expository discourse:Expository writing is probably the most common form of writing.Central to expository writing is grouping, classification and definition. While grouping involves selection, classification involves breaking down of a broad topic into parts.In contrast to these, definition sets limits or boundaries or points out the characteristics that distinguish the thing under discussion from others.Definitions are one of the purest forms of exposition because their purpose is to explain. They answer the basic question €œWhat is it?€ or €œWhat does it mean?€From the above-mentioned points, we can conclude that explanatory or informative discourse is exposition.Additional InformationVarious other forms of discourse are:Narrative discourse: Narration depends chiefly on temporal order, i.e., upon actions in chronological order. The chronological order involves the sequencing of events or actions from beginning to end. A skilled narrator is able to arrange the details in such a way so that a readers interest rises to a climax at some point in the narration. The narration, in turn, can range from storytelling, as in novels and short stories, to anecdotes used for illustration, explanation, or support.Descriptive Discourse: Description also involves narration, but of a different kind. It is a kind of picture making, indicating what someone, something, or someplace, etc. looks like. All descriptions involve spatial dimensions. A description of scenery could either begin with a central focus on a particular detail and then proceed to other things that relate to it, giving us, thereby, a general picture.Argumentative Discourse: In argumentative discourse, the writer argues a case, or expresses an opinion, by looking at a problem from both sides. Any structure representing argumentation must take into account the pro-and-con nature of the argument. Argumentation can be done in three different ways. First, one can give one's own arguments by taking an affirmative position. Second, one can give further evidence to counter-balance the arguments of an opponent. And, third, one can point out the fallacies in ones opponents arguments in order to discredit them.