Probably the most important sentence in an essay is the thesis statement, which is a sentence that conveys the thesis—the main point and purpose of the essay. The thesis is what gives an essay a purpose and a point, and, in a well-focused essay, every part of the essay helps the writer develop and support the thesis in some way.
The thesis should be stated in your introduction as one complete sentence that
identifies the topic of the essay,
states the main points developed in the essay,
clarifies how all of the main points are logically related, and
conveys the purpose of the essay.