On this page we're going to analyze a topic sentence. Consider the following paragraph:

Topic sentences often act like tiny thesis statements. Like a thesis statement, a topic sentence makes a claim—an assertion—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.

Examine the above paragraph. It's about topic sentences. Look at the topic sentence itself:

Topic sentences often act like tiny thesis statements.

That sentence is my claim, or the point I will prove in the rest of the 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—an assertion—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.