通常而言，主題句就是一段話的第一句。后面的句子一般為支持性的細節，以解釋、發展或是支持主題句所表現的主要論點。
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The recent string of corporate scandals provided a rude awakening to the importance of these internal checks. In the case of WorldCom, it was internal auditor Cynthia Cooper who blew the whistle on the company for inflating profits by $3.8 billion. She didn’t intend to be a hero, she said to Time magazine when it named her one of its Persons of the Year. She was just doing her job.
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Chief constables had disapproved of the use of league tables. They complained that they provoked unfair criticism because they did not compare like with like. Mr. Denham said the graphs were easier to comprehend than tables. “As people get familiar” with this type of graphical presentation they will realize it contains a lot of data that can be understood after an initial glance. “ The spidergrams are based on five indicators: reducing crime, investigation crime, public safety, deployment of resources and the view of a focus group of local citizens.
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有時候主題句也會出現在整段話的最后。這樣的結構安排，通常出現在一個討論困難的、不為大眾所接受的話題或者文章的主要目的是為了說服讀者接受某種結論的段落中。因為先把道理說清楚，那么讀者就會比較容易接受新的觀點和看法。