Containing small beginnings and ends, and large middles, Expository paragraphs can probably best be defined using the hamburger as a model in that the top bun is the topic sentence, the one that summarizes the main idea of a paragraph, adds cohesion to the paper the paragraph is found in, makes some kind of claim related to the overall thesis of the paper, and helps organize ideas in the paragraph and the whole paper Topic sentences should also be the catch line that draws the reader's attention and expresses the writer's perspective on the paper being written, therefore, topic sentences need to be clear and concise, as well as present a controlling idea or argument.
The next part of the expository paragraph is the fillings, or body sentences of the paragraph. The first one of these is known as the Directional Sentence that serves the purpose of naming the evidence the writer uses to back up their claim in the order it will appear in the paragraph. This sentence should immediately follow the topic sentence. The rest of the fillings should then contain one or two sentences, for each piece of evidence presented in the Directional Sentence, that use precise words to get right to the point being presented by the writer.
Which leaves the bottom bun to be the concluding sentence that summarizes what the writer has said in a call to action.