What is the main idea of a paragraph typically introduced by?

The main idea of a paragraph is typically introduced by a topic sentence. This sentence serves as a guide for the reader, outlining the primary focus or argument of the paragraph. It encapsulates the overall message and helps to set the tone for the details that follow, making it easier for the reader to understand the context and purpose of the information presented. A well-crafted topic sentence provides clarity and direction, allowing readers to anticipate what supporting details and evidence will be provided to elaborate on the main idea. By establishing this framework, the topic sentence plays a crucial role in effective paragraph structure and coherence.