Topic Sentence Definition

decorative imageJust like a thesis, topic sentences are key elements in college essays. However, while you have only one thesis in an essay, you will have multiple topic sentences in an essay. Topic sentences are like signposts that extract pieces of the thesis idea or angle and let your reader know the part of the thesis angle that you are discussing. They help shape the essay and move it along from one main idea to the next.

Like the thesis, topic sentences themselves have topics and angles. The topic may be the same as the thesis’ topic, but the angle differs depending on the part of the thesis angle the topic sentence is offering. Think of topic sentences in this way: The thesis sentence offers the main idea or insight for the whole essay; a topic sentence offers the main idea or insight for a section of the essay. To use another metaphor, a thesis sentence illuminates the whole space; a topic sentence illuminates one portion of the space.

Thesis Sentence

chandelier with many small lights

Topic Sentence

row of lightbulbs with only one lit

Here’s an example

Thesis sentence:  Trends in home lighting change as aesthetic values respond to social experience; this is most noticeable if you compare lighting trends of the 1960s, 1990s, and today.

Topic Sentence: Lighting in the 1960s was ebullient, in-your-face lighting, with big glass globes and colorful “mod” desk lamps, characterizing both the optimism and rebellion of the decade.

Topic Sentence:  1990s lighting trends focused on both technology, reflecting the new importance of technical advances during that decade, and ornate metallic accents, reflecting wealth and stability, as seen in the trends for track lighting and brass lamps and chandeliers.

Topic Sentence: Today’s lighting trends focus on cleaner lines and softer metallics, characterizing a need for simplicity and calm in an increasingly complex and anxious world.

sign with one arrow pointing right and the other pointing leftIt might be helpful to think of a topic sentence as working in two directions simultaneously. Topic sentences relate the paragraph to the essay’s thesis, and thereby act as a signpost for the argument of the paper as a whole, but they also define the scope of the paragraph or unit of support itself. (A unit of support is made up of multiple paragraphs which support the same topic sentence.)

For example, consider the following topic sentence and supporting paragraph from an essay whose thesis deals (humorously) with ways in which fast-food chains make profits.

Thesis:  Fun can be all-consuming, and we’re fond of consuming “fun.”  Fast-food chains are known for clowning around, adding a dollop for a dollar, including special “forget sauce” in their meals, and playing games with portions, all of which create profits as hefty as our waistlines may become.

Topic sentence and supporting paragraph:

Many fast-food chains make their profits from adding a special ingredient called “forget sauce” to their foods. (This topic sentence extracts one of the ideas from the thesis.  It also controls the paragraph that follows, so that all sentences in the paragraph or unit of support must relate in some way to fast food, profit, and “forget sauce.”) Made largely from edible oil products, this condiment is never listed on the menu. (This sentence fits in with the topic sentence because it is a description of the composition of “forget sauce.”) In addition, this well-kept industry secret is the reason why ingredients are never listed on the packaging of victuals sold by these restaurants. (The transitional phrase “In addition” relates the composition of “forget sauce” to secret fast-food industry practices.) “Forget sauce” has a chemical property which causes temporary amnesia in consumers. (This sentence states the short-term effect on consumers.) After spending too much money on barely edible food bereft of any nutritional value, most consumers swear they will never repeat such a disagreeable experience. Within a short period, however, the chemical in “forget sauce” takes effect, and they can be depended upon to return and spend, older but no wiser. (This sentence describes its longer-term effects and relates back to the thesis sentence, as it discusses profits made from “forget sauce.”)

The following brief video provides a simple way of explaining an important concept about topic sentences, that they link supporting ideas and examples to the thesis throughout an essay and create a logical flow of ideas within an essay.

Note: The content in this video is presented visually. You may listen to this video with audio description.