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Using Topic Sentences to Write Stronger, Better-Organized Scientific Manuscripts

Release Date: June 21, 2012
Category: Manuscript Writing

Key Points Summary

  • Topic sentences establish the point you will discuss in each paragraph and help readers stay focused.
  • Use topic sentences to transition between paragraphs and help shift readers’ focus more smoothly from one point to another.
  • The topic sentence should usually appear at or near the beginning of a paragraph.
  • Effective topic sentences state the topic and also indicate how you will address the topic.
  • Topic sentences should support and advance your claims, not simply repeat your hypothesis.
  • Using topic sentences can keep your manuscript organized and eliminate irrelevant sentences that weaken your paragraphs.

Well-constructed paragraphs are important because they help readers follow your points and understand the reasons for your findings and conclusions. The elements of a well-constructed paragraph are:

  • A topic sentence
  • Focus on a single point of discussion
  • Coherent writing that is easy for readers to understand
  • Completion of the point

Topic sentences establish the point you will discuss in each paragraph. Good topic sentences are the frame upon which you build your manuscript. If you removed everything from your manuscript except the topic sentences, you should have an outline of all your major points.

Placement for Topic Sentences

Readers use topic sentences as mental cues for the information they will read in the rest of the paragraph, so the topic sentence should usually appear at or near the beginning of a paragraph. In addition, if the topic sentence comes first, readers can pick up information about the content of your paper quickly and do not have to search for the main points.

Writing Topic Sentences

To write a topic sentence, think about the information you need to communicate. What point do you want to emphasize? What do you want readers to understand? The answers to these questions will help you formulate appropriate topic sentences. For example, if you are describing a new surgical technique and you want readers to understand how the new technique is better than existing techniques, your topic sentence could be: “This new technique has several important advantages over currently employed techniques.”

You can use the major points of your figures and tables to develop topic sentences. The figures and tables are intended to clearly depict the main points you want to readers to understand, so summarizing the main point of each can help you create topic sentences for paragraphs that describe your most important findings. For example, if Table 1 lists data comparing the outcome of your new surgical technique with outcomes of the existing techniques, your topic sentence for a paragraph that compares the outcomes could be: “We compared the outcome of this new surgical technique with those of several currently employed techniques (Table 1).”

Topic sentences can also help shift your readers’ focus more smoothly from one point to another (also called making a transition). Suppose you have just explained that the new surgical technique offers faster patient recovery, and next you want to say that it also results in fewer complications. Your topic sentence could be: “In addition to faster patient recovery, patients also experience fewer complications with our technique.” This tells the reader, “We are moving on from the topic of faster recovery and will now discuss a different advantage of the technique.”

Setting Expectations with Topic Sentences

Effective topic sentences tell readers what to expect in two ways: they state the topic and indicate how you will address the topic. For example, a topic sentence could say "Our study has several important limitations." This tells readers that the paragraph is going to explain your study's limitations. However, if you write "Our study has several important limitations for populations outside the United States," you tell readers not only that the paragraph is going to explain limitations, but also that you will connect those limitations to how the study's results can be applied.

Using Topic Sentences to Support Your Hypothesis

Topic sentences should contribute to your overall hypothesis or argument. Use topic sentences to introduce the supporting information that advances your point, not to repeat your hypothesis in every paragraph. Here is an example:

      Hypothesis: Surgeons can successfully use our new technique to improve patient outcomes for X surgery.
  Topic sentences: We successfully used the new technique in 100 patients who underwent X surgery in our General Surgery Center since January 2011.
    [This tells readers you will discuss your history of using the technique, which is basic supporting information for your hypothesis.]
    Patients who underwent X surgery using the new technique had a lower rate of complications within the first 60 days than those who underwent surgery employing the techniques we used previously. [This tells readers you will compare the rates of complications to support your claim that the new technique will improve patient outcomes.]
    Patients with certain conditions are not candidates for this technique. [This prepares readers to learn which conditions preclude using the technique, which is important to using the technique successfully.]

Organizing Your Points with Topic Sentences

Topic sentences also help you organize your thoughts so that all discussion of a certain topic is collected in the same paragraph rather than scattered throughout the manuscript. As you write and review your manuscript, ask yourself if each sentence supports the point you make in the topic sentence. If any sentences stray to a different topic, you should move that information to a different paragraph for a full discussion.

For example, consider the stray sentence (italicized) in the following paragraph:

      We successfully used the new technique in 100 patients who underwent X surgery in our General Surgery Center since January 2011. Previously, we used the standard technique for X surgery. Of the 100 patients who underwent X surgery using the new technique, 56 were male and 44 were female. The patients’ ages ranged from 35 to 60 years, but most patients were over 50 at the time of surgery (78 of 100; 78%).

The stray sentence contains important information that readers want to know, but it is not relevant to the point of the paragraph. This paragraph is intended to explain basic information about the patients who underwent surgery using the new technique. The information in the stray sentence is important for readers to understand, but the impact of the paragraph is weakened because readers are distracted by the interjected stray sentence.

Comparing the sentences in each paragraph with the topic sentence will help you identify stray sentences that make your manuscript disorganized and distract from your points. In addition, stray sentences often hint at important points that should receive a full discussion. Pulling stray sentences out into separate paragraphs gives you the opportunity to fully develop your thoughts and ultimately strengthen your manuscript.

More Resources for Writing Topic Sentences

  • Indiana University Writing Tutorial Services. Paragraphs and topic sentences. (accessed 20 Feb 2012).
  • Purdue Online Writing Lab (OWL). Paragraphs and paragraphing. (accessed 20 Feb 2012).
  • University of Toronto University College Writing Centre. Using topic sentences. (accessed 20 Feb 2012).

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