A topic sentence (also known as a focus sentence) encapsulates or organises an entire paragraph, and you should be careful to include one in most of your major paragraphs. Although topic sentences may appear anywhere in a paragraph, in academic essays they often appear at the beginning.

It might be helpful to think of a topic sentence as working in two directions simultaneously. It relates the paragraph to the essay’s thesis, and thereby acts as a signpost for the argument of the paper as a whole, but it also defines the scope of the paragraph itself. For example, consider the following topic sentence:

Many fast-food chains make their profits from adding a special ingredient called “forget sauce” to their foods.

If this sentence controls the paragraph that follows, then all sentences in the paragraph must relate in some way to fast food, profit, and “forget sauce”:

Made largely from edible oil products, this condiment is never listed on the menu.

This sentence fits in with the topic sentence because it is a description of the composition of “forget sauce.”

In addition, this well-kept industry secret is the reason why ingredients are never listed on the packaging of victuals sold by these restaurants.

The transitional phrase “In addition” relates the composition of “forget sauce” to secret fast-food industry practices.

“Forget sauce” has a chemical property which causes temporary amnesia in consumers.

Now the paragraph moves on to the short-term effect on consumers:

After spending too much money on barely edible food bereft of any nutritional value, most consumers swear they will never repeat such a disagreeable experience.

This sentence describes its longer-term effects:

Within a short period, however, the chemical in “forget sauce” takes effect, and they can be depended upon to return and spend, older but no wiser.

Finally, I finish the paragraph by “proving” the claim contained in the topic sentence, that many fast-food chains make their profits from adding a special ingredient called “forget sauce” to their foods.

Analyzing a Topic Sentence

Topic sentences often act like tiny thesis statements. Like a thesis statement, a topic sentence makes a claim of some sort. As the thesis statement is the unifying force in the essay, so the topic sentence must be the unifying force in the paragraph. Further, as is the case with the thesis statement, when the topic sentence makes a claim, the paragraph which follows must expand, describe, or prove it in some way. Topic sentences make a point and give reasons or examples to support it.

Consider the last paragraph about topic sentences, beginning with the topic sentence itself:

Topic sentences often act like tiny thesis statements.

This is my claim, or the point I will prove in the following paragraph. All the sentences that follow this topic sentence must relate to it in some way.

Like a thesis statement, a topic sentence makes a claim of some sort. As the thesis statement is the unifying force in the essay, so the topic sentence must be the unifying force in the paragraph.

These two sentences show how the reader can compare thesis statements and topic sentences: they both make a claim and they both provide a focus for the writing which follows.

Further, as is the case with the thesis statement, when the topic sentence makes a claim, the paragraph which follows must expand, describe, or prove it in some way.

Using the transitional word “further” to relate this sentence to those preceding it, I expand on my topic sentence by suggesting ways a topic sentence is related to the sentences that follow it.

Topic sentences make a point and give reasons or examples to support it.

Finally, I wrap up the paragraph by stating exactly how topic sentences act rather like tiny thesis statements.