主题句(topic sentence)是表达段落主题的句子。它用以概括段落大意，要求全段其他文字都围绕它展开。请看下例：

　　My mother has passed along to me certain rules for getting along with others. Don't argue with parents; they will think you don't love them. Don't argue with children; they will think themselves victimized. Don't argue with spouses; they will think you are a tiresome mate. Don't argue with strangers; they will think you are not friendly. My mother's rules, in fact, can be summed up in two words: Don't argue.

　　主题句中提出的 "certain rules" 指的是什么?展开句中通过四个 "Don't argue --" 逐一加以交代。从结构来看，这是一个比较典型的段落，它包括了主题句，推展句和结论句(即本段中的末句)。

　    主题句的位置

　　主题句通常放在段落的开端，其特点是开门见山地摆出问题，然后加以详细说明。其作用是使文章的结构更清晰，更具说服力，便于读者迅速地把握主题和想象全段的内容。主题句可以放在段中起到承上启下的作用，或放在段尾起概括全段的作用。但初学者比较难于掌握，因而在四级考试中，考生应尽量采用将主题句放在段落开头的写作手法。，

　　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.，

　　这段文字所讲的主要是能源问题。第一句就概括性地提出“我们目前的生活很大程度上依赖于能源”。而随后出现的三句都是具体事例，对第一句进行说明和论述。我们可以断定第一句为该段的主题句(斜体部分)。 ，

　　例2: (主题句)No one can avoid being influenced by advertisements. (推展句1)Much as we may pride ourselves on our good taste, we are no longer free to choose the things we want, for advertising exerts a subtle influence on us. (推展句2)In their efforts to persuade us to buy this or that product, advertisers have made a close study of human nature and have classified all our little weakness.

　　以上这段由三句话组成。第一句是主题句，直截了当指出无人不受广告影响这个主题，接着列举两个推展句对其补充和支持，指出我们已无法自由选择所需的商品，理由是广告商已仔细研究了我们的心理，并完全掌握了我们的弱点。句子衔接自然，步步紧扣主题。

　　 如何写好主题句中的关键词

　　段落的主题句对主题的限定主要是通过句中的关键词来表现的。关键词要尽量写得具体些。对“具体”的要求包括两个方面：一是要具体到能控制和限制段落的发展;二是要具体到能说明段落发展的方法。准确地把握关键词是清楚地表达段落主题、写好段落主题句的重要前提之一。在上面的例1，例2中，主题句的关键词分别为：depends very much on energy; no one can avoid being influenced. 我们再看下列例句：

　　原句1: He can fix a bicycle himself.

　　斜体部分应为主题句中的关键词。但它只是限制了段落发展的部分内容，并没有告诉读者该用哪种方法展开，是用因果关系法还是用分类法?

　　修正：He can fix a bicycle himself in several simple steps. 的

　　修正：There are several reasons why he can fix a bicycle himself.

　　原句2: She tries to improve her looks.

　　斜体部分应为主题句中的关键词。她试着改变她面容的理由是什么?或者她采取什么方法来改善呢?我们无法从关键词中清楚得知。

　　修正：She tries many ways to improve her looks. 的

　　修正：There are some reasons why she tries to improve her looks。

　　 如何写好主题句的中心思想

　　主题句由两部分组成，即主题(topic)和中心思想(controlling idea)。中心思想的作用是导向(control)和制约(limit)。我们前面谈到的关键词就反映了中心思想。所谓导向就是规定段落的发展脉络，所谓制约就是限制主题的覆盖范围，两者不可分割。没有导向，内容就会离题或偏题;没有制约，内容就可能超出一个段落所能容纳的范围。

　　对于初学写作的人来说，“导向”的重要性容易理解，但如果由他们自己来构思一个主题句，就可能忽视“制约”这一面。例如：

　　There are two ways in which one can own a book. The first is the property right you establish by paying for it, just as you have made it a part of yourself and the best way to make yourself a part of it is by writing in it.

　　本段的主题句如果没有in which 引出的定语从句，那么two ways 不仅不能起制约作用，而且也不能起导向作用，句子本身读起来也就使人觉得欠缺点什么。

　　Exercise is beneficial to your heart. A 22-year study was conducted by doctors in California. They found that people who work at physical jobs experience fewer heart attacks than other people. These active people work all the time at moderate speeds, their daily routine gives them an adequate amount of exercise and helps them stay in shape.

　　"Exercise is beneficial"这是毫无疑义的。但主题句中如不加上"to your heart"来加以 control 和 limit，那就流于空泛。

　　因此，紧紧把握主题句中controlling idea的导向和制约作用，是短文写作成功关键之一

　　　    主要推展句

　　主要推展句(major supporting statement)的主要特点是：围绕段落主题句展开的每一个推展句本身都不要求作进一步的说明或证明，句与句之间的关系是相互独立又是互相连接的。

　　例1：(主题句) There are several factors affecting climate. (推展句1)One factor is the mount of sunlight received. (推展句2)Altitude, or the height above sea level, also determines climate. (推展句3)The oceans have an effect on the climate of adjacent land. (推展句4)In addition, climate is influenced by the general circulation of the atmosphere.

　　主题句指出影响气候的几个因素。然后用四个扩展句说明四种因素。第一种是太阳光的接收量，第二种是海拔高度，第三句和第四句分别是海洋和大气环流因素。

　   次要推展句

　　次要推展句(minor supporting statement)是指对主要推展句作进一步的事实分析和举例说明。它从属于某一个或某几个推展句。

　　例2：(主题句)I don't teach because teaching is easy for me. (主要推展句1)Teaching is the most difficult of the various ways I have attempted to earn my living: mechanic, carpenter, writer. (主要推展句2)For me, teaching is a red-eye, sweaty-palm, sinking-stomach profession. (次要推展句1)Red-eye, because I never feel ready to teach no matter how late I stay up preparing. (次要推展句2)Sweaty-palm, because I'm always nervous before I enter the classroom, sure that I will be found out for the fool that I am. (次要推展句3)Sinking-stomach, because I leave the classroom an hour later convinced that I was even more boring than usual.

　　从属于主要推展句2的三个次要推展句起着解释说明作用，分别解释red-eye, sweaty-palm, sinking-stomach的含义，这就更加形象生动地证明了 "teaching is not easy" 这个主题。

　　主要推展句与次要推展句的关系

　　主要推展句与次要推展句的关系(relation)基本可以遵循下面的“三部分”(three-part)规则。

　　1〕每个主要推展句都应该是对主题句中表示主要思想的关键词的直接、明确的说明。

　　2〕每个次要推展句都应该说明它的主要推展句。

　　3〕含有讨论说明或分析的问题通常既要有主要推展素材，又要有次要推展素材。

　　写好推展句的方法

　　主题句及关键词确定后，开始选择和主题有关的信息和素材。实质上，针对关键词测试每一个所选择的素材就是一个分类的过程。有一种常用的方法就是句子展开前加以设问，然后解答，即设问-解答(why-because)的方法。下面我们通过举例来看一看这种分类过程是如何完成的。例3：

　　假设 (suppose) Topic sentence: English is an international language?

　　设问(why) Why can we say English is an international language?

　　解答(because)

　　Because: English is spoken by pilots and airport control operators on all the airways of the world.

　　Because: Over 70 percent of the world's mail is written in English.

　　Because: More than 60 percent of the world's radio programs are in English.

　　Because: Pakistan was once one of the British colonies.

　　Because: Many members of the International Language Society are selected from English-spoken countries.

　　从上面可以看出，最初的三个推展句是和关键词an international language一致的。第四句和主题句不统一，尽管第四句会成为另一主题句(Many Pakistanis speak English)很好的推展句。第五句说服力不强。

　　当然，在写成段落时，没有必要在每个句子开头写上 "because"，但是，在动笔展开句子时，头脑里要想着这个词，这种检验方法能帮助你把注意力集中在某个重心，围绕主题思想层层展开。

　　上面我们讨论了主要推展句的一种展开方法。而展开次要推展句的方法与主要推展句类似，这里我们就不再复述了。

　　　列举法(details)

　　作者运用列举法，是通过列举一系列的论据对topic sentence中摆出的论点进行广泛、全面地陈述或解释，列举的顺序可以按照所列各点内容的相对重要性、时间、空间等进行。，

　　Yesterday was one of those awful days for me when everything I did went wrong. First, I didn't hear my alarm clock and arrived late for work. Then, I didn't read my diary properly and forgot to get to an important meeting with my boss. During the coffee break, I dropped my coffee cup and spoilt my new skirt. At lunch time, I left my purse on a bus and lost all the money that was in it. After lunch, my boss was angry because I hadn't gone to the meeting. Then I didn't notice a sign on a door that said "Wet Paint" and so I spoilt my jacket too. When I got home I couldn't get into my flat because I had left my key in my office. So I broke a window to get in and cut my hand.

　　根据本段主题句中的关键词组everything I did went wrong，作者列举了8点内容，分别由first, then, during the coffee break, after lunch time等连接词语引出，使得该文条理清楚、脉络分明、内容连贯。

　　常用于列举法的过渡连接词有：for one thing , for another, finally, besides, moreover, one another , still another, first, second, also等。，

　　　叙述法(narration)

　　叙述法发展段落主要是按照事物本身的时间或空间的排列顺序，通过对一些特有过渡连接词的使用，有层次分步骤地表达主题句的一种写作手段。用这种方法展开段落，作者能够清楚连贯地交待事物的本末，从而可以使读者可以清晰、完整地理解文章的含义，例如：，

　　In the flat opposite, a woman heard the noise outside. When she looked out through the window, she discovered that her neighbor was threatened by someone. She immediately called the police station. In answer to the call, a patrol police car arrived at the scene of the crime quickly. Three policemen went inside the flat at once, and others guarded outside the building to prevent anyone from escaping.，

　　这段是按照事物发展的先后顺序，叙述从发现案情、报警、到警察赶到、包围现场的过程。全文脉络清晰，叙述的层次感强，结构紧凑。

　　常用于叙述法中的过渡连接词有：first, an the beginning, to start with, after that, later, then, afterwards, in the end, finally等。

　　对比法或比较法(comparison & contrast)

　　将同类的事物按照某种特定的规则进行比较分析是一种常用的思维方法。通过对比，更容易阐述所述对象之间的异同和优缺点，例如：

　　The heart of an electronic computer lies in its vacuum tubes, or transistors. Its electronic circuits work a thousand times faster than the nicer cells in the human brain. A problem that might take a human being a long time to solve can be solved by a computer in one minute.

　　在这段文字上， 作者为了突出电子计算机运行速度之快，首先将它与人脑进行了比较， "-- a thousand times faster than --" ;而后，又将这一概念具体到了 "a problem"上，通过对比使读者从 "-- a long time -- in one minute"上有更加直观的认识。

　　常用于对本法或比较法上的过渡连接词有：than, compared with等。

　　分类法(classification)

　　在阐述某一概念的段落中，常用分类法。通过对概念中所包括的事物进行分门别类，分别加以叙述，使读者有更为清晰的认识，如：

　　Ever since humans have lived on the earth, they have made use of various forms of communication. Generally, this expression of thoughts and feelings has been in the form of oral speech. When there is a language barrier, communication is accomplished through sign language in which motions stand for letters, words and ideas. Tourists and the people unable to hear or speak have had to resort to this form of expression. Many of these symbols of whole words are very vivid and exact and can be used internationally; spelling, however, cannot. Body language transmits ideas or thoughts by certain actions, either intentionally or unintentionally. A nod signifies approval, while shaking the head indicates a negative reaction. Other forms of nonlinguistic language can be found in signal flags, Morse code, and picture signs.

　　在该段中为了说明topic sentence中的 "various forms of communication"，作者将其分为oral speech, sign language, body language及other forms of nonlinguistic language，并逐加阐述。

　　采用这种方法的段落并没有标志突出的连接词，所述各项均为平行并列关系，所以没有明显的主次之分。

　　因果分析法(cause and effect)

　　在阐述某一现象的段落中，常采用因果分析法。例如：

　　The role of women in today's society is changing. One reason is that women have begun to assert themselves as independent people through the women's movement. Also, women are aware of the alternatives to staying at home. Another reason is that increasing numbers of women who enter new fields and interests serve as role models for other women. Moreover, men are becoming more conscious of the abilities of women and have begun to view their independence positively.

　　本段中，主题句提出了一种社会现象，推展句则对产生这种现象的原因作出各种解释。 常用于因果分析法的连接词有：because, so, as a result等。

　　定义法(definition)

　　在科普文章的写作中，定义法是必不可少的。通过下定义，可以使读者对该事物有一个更直接的认识。

　　Automation refers to the introduction of electronic control and automation operation of productive machinery. It reduces the human factors, mental and physical, in production, and is designed to make possible the manufacture of more goods with fewer workers. The development of automation in American industry has been called the "Second Industrial Revolution".

　　这一段文字使我们了解了 "automation" 和 "Second Industrial Revolution" 两个概念，分别由 "refers to" 和 "been called" 引出。

　　常出现在定义法中的词语有：refer to, mean, call等。

　　重复法(repetition)

　　句子的一部分反复出现在段落中，这就是重复法。它往往造成一种步步紧逼的气氛，使文章结构紧凑，有感染力。比如：

　　Since that time, which is far enough away from now, I have often thought that few people know what secrecy there is in the young, under terror. I was in mortal terror of the young man who wanted my heart and liver; I was in mortal terror of my interlocutor with the iron leg; I was in mortal terror of myself, from whom an awful promise had been extracted; --

　　该段中反复应用了I was in mortal terror of …我经常处于恐怖之中。

　　以上， 我们结合具体文章讨论了展开段落的几种方法。在实际写作中，我们往往不必拘泥于一种写作方法，而是将若干方法穿插在一起，使文章有声有色。

　　结尾段

　　我们知道文章的开头很重要，因为好的开头可以吸引读者、抓住读者的注意力。同样，文章的结尾也很重要，好的结尾会使读者对全文的中心思想留下深刻的印象，可以增添文章的效果和说服力，让人深思，回味无穷。确切地说，结尾的作用就是概括全文内容，进一步强调或肯定文章的中心思想，使读者加深印象;有时也用于展望未来，提出今后方向或令人深思的问题给读者留下回味和思考的余地。

　　但是，如何才能写好文短文的结尾呢? 下面就介绍几种写结尾段最常用的方法：，

　　1.重复中心思想: 回到文章开头阐明的中心思想或主题句上，达到再次肯定和强调的效果。

　　(例1)A sense of humor is really one of the keys to happiness. It gives zest to life to make it worth living.

　　(例2)With all these benefits, it is no wonder that sports and games have now become more popular with people than ever.，

　　2.作出结论: 文章最后用几句话概括全文内容，并进一步肯定文章的中心思想或作者的观点。

　　(例1)In conclusion, a good teacher-student relationship can be mutual beneficial. The students gain knowledge eagerly and enjoyably, and the teacher gains satisfaction from his job.

　　(例2)On the whole there are more advantages than disadvantages in the use of TV. Yet different people may have different attitude toward TV. But we must realize that television in itself is neither good nor bad. Its value to people and society depends on how we look at it.，

　　3.应用引语: 用格言、谚语或习语总结全文，既言简意赅又有更强的说服力。

　　(例1)If you have anything to do, try to do it yourself, for that is the safest way to

　　permanent success. Remember the famous saying. "God helps those who help themselves."

　　(例2)If we stick to studies day after day, there is nothing that can't be achieved. As an old saying goes: "Constant dropping of water wears away a stone."，

　　4.用反问结尾: 虽然形式是问句，但意义却是肯定的，具有明显的强调作用，引起读者思考。

　　(例1)Therefore, listening skills must be consciously improved. Since it is such an important means of learning and communication, why should we not develop this ability as far as possible?

　　(例2)So，what can we benefit from wealth if we do not have health?，

　　5.提出展望或期望: 表示对将来的展望或期待读者投入行动。

　　(例1)I am sure that Chinese will become one of the most important languages in the world in the next century. As China will open further to the outside world the language is sure to be spread world widely.

　　(例2) If everyone has developed good manners, people will form a more harmonious relation. If everyone behaves considerately towards others and social ethics people will live in a better world. With the general mood of society improved, there will be a progress of civilization.

　　以上介绍了几种写结尾段最常用的方法，但到底选择何种方法结尾还得根据文体来决定。平铺直叙的记叙文，往往在故事或事实情节讲完时文章也就自然结束了，而说理性和逻辑性较强的说明文和议论文都应有一个正式的结尾。希望以上介绍的几种方法能对大家写好结尾有所帮助。