無論是中文還是英語抑或其他語言，我們知道寫文章勢必要有一個中心思想，而每個段落只能有一個主題(central idea)，它用一個句子加以表達，就是主題句。幾個主題句的精彩寫作不僅會讓文章條理分明，更能夠很好的詮釋文章主題思想，可謂是文章的架構(gòu)靈魂，所以，寫好主題句對一篇文章的好壞有著至關(guān)重要的作用。
　　首先，充分了解主題句。
　　定義：主題句為一個完整的句子，用以概括、敘述和說明該段的主題。
　　位置：主題句一般位于段首，也可置于段尾或段中，考生比較好放在段首，這樣較易掌握和構(gòu)思。
　　例如：
　　位于段首：在英文中，大部分段落的第一句便是主題句。開門見山地提出問題，后面的擴展句圍繞主題句加以說明、支持、補充和解釋。
　　An important part of police strategy, rapid police response is seen by police officers and the public alike as offering tremendous benefits. The more obvious ones are the abilities of police to apply first aid life saving techniques quickly, and the greater likelihood of arresting people who may have participated in a crime. It aids in identifying those who witnessed an emergency or crime as well as in collecting evidence. The overall reputation of a police department too is enhanced if rapid response is consistent and this in itself promotes the prevention of crime. Needless to say rapid response offers the public some degree of satisfaction in its police force.
　　位于段尾：主題句位于段尾便于總結(jié)全段的內(nèi)容，給讀者以深刻的印象，是寫作中的一種演繹方法。
　　At present rates of demand, the world has enough oil to last for more than 40 years, enough gas for more than 60 years and enough coal for more than 230 years. Naturally, demand will increase; but so will reserves as companies explore more widely and costs fall. Since 1970 viable reserves of oil have almost doubled while those of gas have leapt three-fold. One distant day a crunch will come, but as it approaches fossil-fuel prices will rise, making alternative forms of energy, perhaps including nuclear power, competitive. That is no reason to spend on nuclear now.
　　位于段中：位于段中的主題句起承上啟下的作用，這類主題句多起轉(zhuǎn)折作用，一般由“but, however, yet, anyhow, nevertheless”等詞連接，用于引起下文。
　　What we teach ourselves sometimes, indeed, is more useful than what we learn from others. Some great men had little or no schooling. But these great men probably studied harder by themselves than most boys do in school. The greatest minds do not necessarily of those who have never been able to distinguish themselves at school, have been very successful in life later. It has been said that Wellington and Napoleon were both dull boys at school, and so were Newton and Albert Einstein.
　　無主題句：有的段落中無主題句，段落的主題思想通過文章內(nèi)容來提示，這種方法能促使讀者對文章內(nèi)容進行思考和分析，但考生一般不宜在考試中采用這種方法：
　　Money may be deposited or withdrawn from branches of the credit unions and banks during business hours from Monday to Friday (but not on public holidays) or 24 hours a day from the many on-campus automatic teller machines. Business hours for financial institutions vary, but credit unions are usually open from 9 am to 5 pm weekdays, and, generally, banks are open from 9.30 am to 4 pm (5 pm on Fridays). Some services are available on Saturday mornings in selected areas. While prices often compare favorably with prices overseas, because Australia is a large and exciting country it is very easy to overspend, especially if on a tight budget.
　　其次，如何寫好主題句。
　　寫好主題句的方法：
　　1)主題句要概括一定內(nèi)容，不要空泛，否則擴展句將難以說明和支持它，例如：
　　空泛：English language is very important.
　　概括：English language is very important in our daily life.
　　空泛：The Olympic Games are exciting.
　　概括：In the Olympic Games the football teams from many countries compete intensely.
　　2)盡量使用簡單句或簡潔明了的句子，例如：：
　　簡潔：Collecting stamps is her hobby.
　　復雜: She likes collecting stamps which is her hobby.
　　簡潔: I enjoyed watching Gone with the wind very much.
　　復雜：Gone with the wind was a good film which I enjoyed watching very much.
　　3)主題句應該做到句子完整和表達的主題思想完整，：例如：
　　不完整：How to write a composition.
　　完整：How to write a composition is not an easy thing to talk about.
　　不完整：If the weather had been fine.
　　完整：If it had been fine, we would have had a good time.
　　4)關(guān)鍵詞是直接表達主題的詞匯，它決定段落的內(nèi)容和展開的方法，引導整個段落的發(fā)展，例如：
　　There are several ways to boil the water.
　　The task can be finished in three steps.
　　There is a new method to reduce the cost.