What is the main purpose of a topic sentence in a piece of nonfiction writing?

The main purpose of a topic sentence in a piece of nonfiction writing is to state the main idea of the paper. A topic sentence serves as a guiding statement for the paragraph it introduces, encapsulating the central theme or argument that will be explored in that section. This allows readers to grasp the focus of the paragraph immediately, which enhances comprehension and keeps the writing organized. By clearly presenting the main idea, the topic sentence helps readers understand what to expect and how various pieces of information will relate to that core concept. In this way, it establishes a strong foundation for the discussion that follows, making the writing clearer and more effective.