The foundation of a good paragraph is the topic sentence, which expresses the main idea of the paragraph. The topic sentence relates to the thesis, or main point, of the essay and guides the reader by signposting what the paragraph is about. All the sentences in the rest of the paragraph should relate to the topic sentence.

Function and Elements of a Topic Sentence

A topic sentence is usually the first sentence of a body paragraph. The purpose of a topic sentence is to identify the topic of your paragraph and indicate the function of that paragraph in some way.

In order to create an effective topic sentence, you should do the following:

1. Use a transitional device to effortlessly segue from the idea discussed in the previous paragraph.

When choosing a transitional device, you should consider whether your new paragraph will build onto the topic of your previous paragraph, begin to develop a new key idea or sub-claim, or present a counterargument or concession.

2. Clearly identify the key idea or sub-claim that you intend to expand upon in your new paragraph.

Even if you are building onto the idea of the previous paragraph, you will still need to identify the sub-claim in your topic sentence. When constructing a topic sentence, you may feel as though you are stating the obvious or being repetitive, but your readers will need this information to guide them to a thorough understanding of your ideas.

3. Make a connection to the claim you make in your thesis statement.

It might help to think of your topic sentence as a mini thesis statement. In your body paragraph, you should be expanding upon the claim you make in your thesis. For this reason, you should link your topic sentence to your thesis statement. Doing so tells your readers, “This is the point I mentioned in my thesis that I now intend to support and either prove or explain further.”

Developing a Topic Sentence

Pick up any newspaper or magazine and read the first sentence of an article. Are you fairly confident that you know what the rest of the article is about? If so, you have likely read the topic sentence. An effective topic sentence combines a main idea with the writer’s personal attitude or opinion. It serves to orient the reader and provides an indication of what will follow in the rest of the paragraph. Read the following example: Creating a national set of standards for math and English education will improve student learning in many states.

This topic sentence declares a favorable position for standardizing math and English education. After reading this sentence, a reader might reasonably expect the writer to provide supporting details and facts as to why standardizing math and English education might improve student learning in many states. If the purpose of the essay is actually to evaluate education in only one particular state, or to discuss math or English education specifically, then the topic sentence is misleading.

Main Idea versus Controlling Idea

Topic sentences contain both the main idea  (the subject, or topic that the writer is discussing) and a controlling idea (the writer’s specific stance on that subject). Just as a thesis statement includes an idea that controls a document’s focus, a topic sentence must also contain a controlling idea to direct the paragraph. Different writers may use the same main idea but can steer their paragraph in a number of different directions according to their stance on the subject. Read the following examples.

• Marijuana is a destructive influence on teens and causes long-term brain damage.
• The antinausea properties in marijuana are a lifeline for many cancer patients.
• Legalizing marijuana would create a higher demand for Class A and Class B drugs.

Although the main idea—marijuana—is the same in all three topic sentences, the controlling idea differs depending on the writer’s viewpoint.

Characteristics of a Good Topic Sentence

Five characteristics define a good topic sentence:

1. A good topic sentence provides an accurate indication of what will follow in the rest of the paragraph.

Weak example: People rarely give firefighters the credit they deserve for such a physically and emotionally demanding job. (The paragraph is about a specific incident that involved firefighters; therefore, this topic sentence is too general.)

Stronger example: During the October riots, Unit 3B went beyond the call of duty. (This topic sentence is more specific and indicates that the paragraph will contain information about a particular incident involving Unit 3B.)

2. A good topic sentence contains both a topic and a controlling idea or opinion.

Weak example: In this paper, I am going to discuss the rising suicide rate among young professionals. (This topic sentence provides a main idea, but it does not present a controlling idea, or thesis.)

Stronger example: The rising suicide rate among young professionals is a cause for immediate concern. (This topic sentence presents the writer’s opinion on the subject of rising suicide rates among young professionals.)

3. A good topic sentence is clear and easy to follow.

Weak example: In general, writing an essay, thesis, or other academic or nonacademic document is considerably easier and of much higher quality if you first construct an outline, of which there are many different types. (This topic sentence includes a main idea and a controlling thesis, but both are buried beneath the confusing sentence structure and unnecessary vocabulary. These obstacles make it difficult for the reader to follow.)

Stronger example: Most forms of writing can be improved by first creating an outline. (This topic sentence cuts out unnecessary verbiage and simplifies the previous statement, making it easier for the reader to follow.)

4. A good topic sentence does not include supporting details.

Weak example: Salaries should be capped in baseball for many reasons, most importantly so we don’t allow the same team to win year after year. (This topic sentence includes a supporting detail that should be included later in the paragraph to back up the main point.)

Stronger example: Introducing a salary cap would improve the game of baseball for many reasons. (This topic sentence omits the additional supporting detail so that it can be expanded upon later in the paragraph.)

5. A good topic sentence engages the reader by using interesting vocabulary.

Weak example: The military deserves better equipment. (This topic sentence includes a main idea and a controlling thesis, but the language is bland and unexciting.)

Stronger example: The appalling lack of resources provided to the military is outrageous and requires our immediate attention. (This topic sentence reiterates the same idea and controlling thesis, but adjectives such as appalling and immediate better engage the reader. These words also indicate the writer’s tone.)

 Continue Reading: 9.3 Developing Paragraphs