What is the purpose of a topic sentence in a paragraph?

The purpose of a topic sentence in a paragraph is to state the main idea of that paragraph. It acts as a guiding statement that encapsulates the central theme or point that will be elaborated upon in the following sentences. By clearly presenting the main idea, the topic sentence helps readers understand what to expect from the paragraph, thereby enhancing comprehension and focus.

For instance, if a paragraph discusses the benefits of exercise, the topic sentence might say something like, "Regular exercise significantly improves physical health and mental well-being." This clear declaration sets the stage for supporting details and examples that will follow, reinforcing the main idea throughout the paragraph.