Topic Sentence Elements
A topic sentence sets up the paragraph, explaining the concept or main idea of the paragraph. For instance, an essay explaining the differences between gaming systems might have a body paragraph that begins, "The Gadmark system costs much less than the FX4," telling the reader this paragraph will focus on price differences. If the paragraph makes up part of the body of an essay, the topic sentence also needs to connect to the thesis. This gaming example relates to a thesis that establishes the Gadmark as a better choice than the FX4 due to various issues including price. The topic sentence should identify the part of the thesis that is the focus of the paragraph.
Transitional Phrases or Words
If a paragraph follows another as part of the body of an essay, the topic sentence should also include a transition, a word or phrase that illustrates the relationship between the paragraph and any previous body paragraphs. A paragraph transition may indicate contrast ("on the other hand" or "however"), addition ("furthermore"), continuation ("similarly") or other connections. Writers also employ key word repetition, parallel structures or pronoun substitution to connect ideas. For example, if the first body paragraph in the gaming contrast paper focuses on price, the second could start, "Not only does Gadmark cost less, but the company also offers better customer service than the FX4 company." The transitional phrase at the beginning of the sentence ties the paragraphs together.