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Mastering topic sentences

Have you ever been to a new country where you couldn’t understand the road signs? Perhaps you were somewhere remote with no road signs at all (or no road). It’s not fun getting lost. The same goes for the reader navigating a piece of writing with poorly written topic sentences – the road signs of an essay. They guide the reader, helping them understand the direction of each paragraph.

The topic sentence comes first

Can you spot the issue with the topic sentence below in an essay about global food consumption? You may have to look hard to even find the topic sentence itself…

Raising livestock requires large quantities of feed and this puts strain on natural resources. In addition, the decomposition of manure releases carbon dioxide which contributes to climate change. There is broad agreement among environmentalists that the meat industry is a major contributor to environmental degradation.

Problem: The topic sentence – the last line – comes too late in the paragraph.

Solution: The topic sentence needn’t always be the opening sentence. However, if you are offering examples, as in the above, it’s advisable to start with the topic of the paragraph, followed by supporting examples, research, statistics, or case studies. Here’s a better version:

There is broad agreement among environmentalists that the meat industry is a major contributor to environmental degradation. For example, raising livestock requires large quantities of feed and this puts strain on natural resources. In addition, the decomposition of livestock manure releases carbon dioxide which contributes to climate change.

The topic sentence is clear

Let’s examine the sentences below (from University of Houston-Victoria). Select which sentence is more focused, and therefore effective.

  • Today’s technology is affecting people’s learning.
  • Today’s technology forces young people to improve their skills through ongoing training.

Problem: The first topic sentence is vague, because it’s not clear what the paragraph is going to be about. Technology could be affecting learning in a million ways. On the other hand, the second topic sentence is much clearer.

Solution: Think of your topic sentence as a mini thesis which states the goal of the paragraph. The second sentence clarifies the writer’s point of view and so the direction of the paragraph is evident. Then, the writer supports the topic sentence with specific examples and explanations. This helps the reader know what to expect and where the paragraph is heading.

Here are more examples of making the topic of the sentence clearer.

  • Home ownership is good for society. [How is home ownership good for society?] → There are social and economic benefits to home ownership.
  • People abuse animals in experiments. [Who? What experiments?]. → Animals are often harmed by the cosmetic industry in experiments to test their products.
  • Public schools are good. [“Good” is a vague word]. → According to research, learners at public schools excel as much academically as private school learners.

Include both a topic and a controlling idea

A topic sentence should also have a “controlling idea” that gives focus and guides the supporting sentences in the rest of the paragraph.

So, to summarise, a topic sentence should consist of two elements.

Problem: The supporting sentences are unrelated to the specific focus in the controlling idea. Check the example, although the topic is somewhat related, the examples are not relevant. 

Chocolate is not only delicious; it also has physiological effects. Junk food in general can be consumed as a comfort food. Even though we know chips, chocolate, and sweets are unhealthy, they can give us a temporary lift when we feel depressed or bored.

The reader never finds out about what the physiological effects of chocolate are as promised. In addition, suddenly the writer starts talking not just about chocolate but everything else, and therefore the paragraph loses direction.

Solution: The controlling idea should inform the specific supporting sentences that follow as per the below example.

Chocolate is not only delicious; it also has physiological effects. Chocolate releases endorphins, which are feel-good chemicals. It also contains caffeine, which provides us with energy. In addition, real dark chocolate contains a cannabinoid, which can provide a hypnotic effect when consumed in significant quantities.

Therefore, the two parts of the topic sentence are necessary. Firstly, the topic (in this case chocolate). Secondly, the controlling idea (in this case the physiological effects) which set the parameters and limit the scope of the paragraph.

The controlling idea can control the supporting sentences and unify the paragraph by setting limitations. For instance:

When preparing a research report, you must complete three sections. Here “research report” is the topic, while “three sections” is the controlling idea. The reader can then predict that the paragraph will describe these three sections.

Phew! After travelling tricky highways with our new-and-improved GPS, we have arrived safely. The full essay contains many paragraphs, each with a clear topic sentence, which help the reader navigate the essay.


By Leigh-Anne Hunter

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