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http://www.answers.com/topic/topic-sentence
A topic sentence is a vital component of a paragraph and serves as a concise statement that defines the main idea or point of that particular paragraph. It is usually found at the beginning of the paragraph and acts as a focal point, summarizing the content that follows. The topic sentence aims to present the overall theme of the paragraph and provide a clear preview of what the reader can expect to find within the subsequent sentences.
