The body of an essay includes many paragraphs that each discuss a new topic to substantiate the essay’s thesis statement (i.e. answer the essay question). Before you start writing a paragraph, it is important to have a topic sentence to unify the paragraph’s content and to ensure the paragraph discusses the topic coherently.
A topic sentence is a single sentence that states the main point of a paragraph. It acts like a thesis statement for just that paragraph. It must be presented at the beginning of a paragraph to tell the reader what the topic of the paragraph is and how the paragraph will discuss it. Another important function of a topic sentence is to prove the essay’s thesis statement. It can also specify the order of the content of a paragraph. This way, the reader can see the organisation of your essay because it will be written in an organised and smooth way, without illogical or sudden shifts or jumps.
For example, if you were writing an essay on the causes of the Holocaust in Germany and your thesis statement was ‘There were multiple complicated and inter-related causes of the Holocaust, including the economy of Germany, the ideology of the fascists and Hitler’s personal racism’, then from this thesis statement, your first topic sentence might be:
The most significant cause of the Holocaust was the economic state of Germany.
This topic sentence tells the reader what the paragraph will discuss. After this topic sentence, you can give background information. Then you start to discuss the topic by applying facts, incidences, argument, analysis or examples from your research. In the final step of writing a paragraph, you should wrap up the connection between your discussion in the paragraph and the topic sentence of the paragraph to ensure the main message of this paragraph stays in the reader’s mind.
Once you have finished discussing the economy of Germany in relation to how it caused the Holocaust, you would move on to the next cause of the Holocaust that you gave in your thesis statement (which was presented in your introduction). In order to transition smoothly from one topic to the next, and to explain to the reader why you are discussing a new topic, you would need to begin your next section with a topic sentence such as:
Another important cause of the Holocaust was the ideology of the Nazi Party.
This signals that you are discussing a new topic, which is the ideology of the Nazi Party, and explains that you are discussing it because it answers your essay question.
If you read all your topic sentences in isolation, you should be able to see an outline of your essay’s argument.
Updated 06 October 2018