Basic structure: Every paragraph, no matter what kind it is or what topic it develops, consists of the same basic structure. According to one English manual, “a paragraph is an organized unit of thought that develops one main idea” (Rod and Staff English Handbook, p. 154). The paragraph contains three basic parts: a topic sentence, a body, and a concluding sentence. The “one main idea” appears in the topic sentence. Several sentences designed to support this main idea form the body of the paragraph, and a concluding sentence briefly restates the main thought, but in different words. This pattern remains constant through every paragraph, including each of the types listed below.
Notice that, in the preceding paragraph, the topic sentence introduces one main idea (that every paragraph has a certain kind of structure). Notice also that the next four sentences develop this main idea by defining a paragraph, articulating its parts, and developing that articulation more fully. And finally, observe that the concluding sentence restates the main idea, not by parroting the same words, but by explaining how the main idea applies to some further element (in this case, the paragraph-types you are about to study).
Unity: When a paragraph displays this three-part structure, then every sentence “relates to” the one main idea by either supporting, explaining, or illustrating the topic sentence (Rod and Staff English Handbook, p. 157). Such a paragraph, containing one well-demonstrated idea, is unified. All good writing contains unified paragraphs. Without paragraph unity, your writing will be sloppy and confusing.
Transition words: A good paragraph uses transition words to link one idea to the next. By a transition word I mean words such as also, additionally, likewise, furthermore, although, otherwise, in fact, for example, as a result, or therefore. Use words like these carefully and intentionally, judging when and where a transition word is necessary. Do not put them in every sentence, or your writing will sound clunky. (See Rod and Staff English Handbook, p. 160.) Also remember that some transition words sound best at the beginning of the sentence, while others (like however) sound better in the middle or after a prepositional phrase. Use your ear to determine whether the transitions sound smooth or forced.
In the following four sections, you will learn eight ways to develop (that is, to articulate and defend) the topic sentences of your paragraphs. Each of these methodologies will require you to use the three-part structure, to achieve paragraph unity, and to employ transition words.