A topic sentence is a clear statement that expresses the main idea of a paragraph. It usually appears at the beginning of the paragraph and helps readers understand what to expect. For example, in a paragraph about dogs, a topic sentence might state, "Dogs are known for their loyalty and companionship."
Effective topic sentences guide the reader through the text by summarizing the key point. They can also help organize thoughts and maintain focus on the subject. For instance, a topic sentence about climate change could be, "Climate change poses significant challenges to global ecosystems."