By itself, a topic sentence will not usually fully clarify an idea or convince readers. Supporting sentences can explain, prove, or enhance the idea in the topic sentence. For example, in a persuasive essay about raising the wage for certified nursing assistants, a paragraph might focus on the expectations and duties of the job, comparing them to those of a registered nurse. Needless to say, a single topic sentence that lists the certified nursing assistant’s duties will not give readers a complete enough idea of what these healthcare professionals do. If readers do not have plenty of information about the duties and the writer’s experience in performing them for what they consider inadequate pay, the paragraph fails to do its part in convincing readers that the pay is inadequate and should be increased.

In informative or persuasive writing, a supporting sentence usually offers one of the following:

• Fact: Many families now rely on older relatives to support them financially.
• Statistic: Nearly 10 percent of adults are currently unemployed in the United States.
• Quotation: “We will not allow this situation to continue,” stated Senator Johns.
• Anecdote or example: Last year, Bill was asked to retire at the age of fifty-five.

The type of supporting sentence you choose will depend on what you are writing and why you are writing. For example, if you are attempting to persuade your audience to take a particular position, you should rely on facts, statistics, and concrete examples, rather than personal opinions. Personal testimony in the form of an extended example can be used in conjunction with the other types of support. Let’s look at a sample paragraph as a list of all the elements we’ve just discussed, plus a concluding sentence, which we’ll discuss below.

Concluding Sentences

Paragraphs do not necessarily need concluding sentences.  However, a concluding sentence can help if you think your readers need a reminder of what the main point was or what we have learned from the paragraph. If the material in the paragraph taken together seems to logically imply an idea, we can name that idea in the concluding sentence.  This might take the form of a prediction, suggestion, or recommendation about the information in the paragraph. For example, a paragraph on childhood obesity might conclude, “These statistics indicate that unless we take action, childhood obesity rates will continue to rise.”

If we repeat the main point, we should express it in different words to avoid sounding too repetitive. For example, let’s compare the topic sentence and concluding sentence from the first example on hybrid cars:

Notice the use of the synonyms advantages and benefits. The concluding sentence reiterates the idea that owning a hybrid is advantageous without using the exact same words. It also summarizes two examples of the advantages covered in the supporting sentences: low running costs and environmental benefits.

Paragraph Length

Writers often want to know how many words a paragraph should contain. There is no set number; a paragraph needs to develop an idea enough to satisfy the writer and readers. Paragraphs can vary in length from one or two sentences to over a page; however, in most college assignments, successfully developed paragraphs usually contain one hundred to two hundred fifty words and span one-fourth to two-thirds of a typed page.

If a paragraph is more than a page long, consider providing a paragraph break for readers. Look for a logical place to divide the paragraph, and then revise the opening sentence of the second paragraph to maintain coherence.

Occasionally a short paragraph may serve to emphasize an idea, but a series of short paragraphs can be confusing and choppy. Examine the content of the paragraphs and combine them with related ideas or develop each one further.