主題句是表達段落主題的句子。它用以概括段落大意，要求全段其他文字都圍繞它展開。請看下例：
My mother has passed along to me certain rules for getting along with others. Dont argue with parents; they will think you dont love them. Dont argue with children; they will think themselves victimized. Dont argue with spouses; they will think you are a tiresome mate. Dont argue with strangers; they will think you are not friendly. My mothers rules, in fact, can be summed up in two words: Dont argue.
主題句中提出的certain rules指的是什麼?展開句中通過四個Dont argue -- 逐一加以交代。從結構來看，這是一個比較典型的段落，它包括了主題句，推展句和結論句。
1.1 主題句的.位置
主題句通常放在段落的開端，其特點是開門見山地擺出問題，然後加以詳細說明。其作用是使文章的結構更清晰，更具說服力，便於讀者迅速地把握主題和想象全段的內容。主題句可以放在段中起到承上啓下的作用，或放在段尾起概括全段的作用。但初學者比較難於掌握，因而在六級考試中，考生應儘量採用將主題句放在段落開頭的寫作手法。
例1: Our life today depends very much on energy. In towns and in villages, on farms and in factories, machines have made life easier than it used to be. The machines use energy, and energy is needed for heating, lighting, communications, carrying goods -- everything. Factories and industrial plants use a great deal of energy to make the things that we use and buy and sell.，
