Here's why:
* Direction: The topic sentence sets the course of the paragraph. It clearly states the main idea or argument that the paragraph will explore.
* Focus: It acts as a lighthouse, keeping the paragraph focused on the central theme. All other sentences in the paragraph should directly support and develop the topic sentence.
* Preview: It offers a preview of the territory that will be covered in the paragraph, making it easier for the reader to follow the discussion.
* Connection: It acts as a bridge, connecting the paragraph to the larger argument of the essay.
Think of it like this:
* Topic sentence: "The internet has revolutionized communication."
* Supporting sentences: Discuss specific ways the internet has changed communication (e.g., instant messaging, video calls, social media).
* Overall paragraph: The paragraph explores the impact of the internet on communication.
Without a strong topic sentence, a paragraph would be like a ship without a captain, lost and directionless.