主题句注意事项

结构完整的段落大多由三部分组成：

一、主题句

主题句是概括段落中心思想，反映作者写作意图的一个概括性的句子，是段落的核心所在。所以，写好主题句是写好一个段落的前提。

1.段落主题句的位置及其作用

主题句通常由主题和作者的观点两部分组成，作为段落传递信息的出发点，简明扼要地告诉读者段落的线索和范围。但是，主题句的位置并不是固定不变的，它可以位于段首，也可以位于段中、段尾。主题句位于段首的情况比较多见。段首主题句开门见山，直接点明段落主题，有助于确定段落的主线，使各个发展句围绕段落主题自然展开；段尾主题句具有结论作用，是对前面句子的归纳总结。

2.段落主题句的写作方法

主题句的作用是要告诉读者该段的主题思想，该段将围绕这个主题思想逐步展开、定义、论述、分类、解释和举例说明等，所以，段落主题句中必须包含一个主导思想，这是一个等待发展的思想，也是段落的主旨所在。同时，段落主题句不能写得太笼统，也不能涉及面太窄。一个段落的容量是有限的，如果主题句限定范围太宽，其内容就无法在一个段落中阐述清楚；如果限定范围太窄又不利于段落的发展。段落主题句所限定的内容必须符合段落写作的目的，有助于段落的铺开和抒发。例如：

T elevision is very important. 这个句子太泛，没有表达一个清楚的主题思想，做主题句不大合适。可以改为：Television plays an educational role in our daily life.

Big cities have traf fic problems.这个句子如果用做主题句也没有表达出明确的主题思想，范围限得过宽，抓不住段落主线，不好下笔扩展段落。可改为：Traffic problems in big cities are serious, which can be found in several ways.

He encountered an old friend yesterday.这是一个描写细节的句子。由于涉及面太窄而不利于展开讨论，不适合做主题句。

I go to college to make friends.如果作为段落的主题句就显得范围太窄了，作者发挥的余地太小，段落不容易写好。可改为：Going to college, I can learn more and make new friends.

二、扩展句

扩展句是用来支持或说明主题句的，是段落主题句的延伸和发展，起着辅助主题句、推展段落中心的作用，对主题句表达的中心思想或举例说明、或细致描写、或详细解释阐述和论证，使读者能够清晰地理解和信服地接受作者所表达的意思。

扩展句一般要具备这样的特点：（1）清晰、详实，有较强的说服力，能清楚地表达思想；（2）条理分明，脉络清晰。上一句要为下一句铺平道路，下一句是上一句的自然延伸，一步一步地论述或叙述主题。

一个段落通常有若干个扩展句。这些扩展句可以处于同一个层次，共同来为主题句服务；也可以在一级扩展句之下用二级扩展句来支持一级扩展句，从而构成扩展句之间的层次关系。但在段落中如果有多个不同层次的扩展句时，必须要合理地安排它们，既要作到简洁清晰、意义连贯、合乎逻辑，又要作到层次分明并紧紧地围绕主题句，为主题句服务；同时还要注意一级扩展句、二级扩展句等和主题句之间的关系。一级扩展句为主题句服务，二级扩展句支持一级扩展句来说明或论证主题句。

Strong in action, gentle in method.——行动要坚强，方式要温和。请看下面的例子：

（1）Money spent on advertising is money spent as well as any I know of.（2）It serves directly to assist a rapid distribution of goods at reasonable prices thereby establishing a firm home market and so making it possible to provide for export at competitive prices. （3）By drawing attention to new ideas, it helps enormously to raise standards of living. （4）By helping to incr ease demand, it ensures an increased need for labor, and is therefore an effective way to fight unemployment. （5）It lowers the costs of many services: without advertisements your daily newspapers would cost four times as much, the price of your television license would need to be doubled, and travel by bus or tube would cost 20 percent more.

这个段落中的句（1）是段落主题句，提出观点：“花钱做广告是我所知道的最好的花钱方式。句（2）、（3）、（4）和（5）都是扩展句，处在同一层次上，进一步阐述和说明主题句，即通过列举广告给社会带来的好处来说明为什么花钱做广告是最好的花钱方式。

(1)The computer finds many applications in all fields. (2)Computers are now doing almost everything from diagnosing hospital patients to running nuclear pow er stations. (3)In any field where information is collected, processed, stored, and retrieved, computers are being used more and more. (4)Computers are also used as an aid to design planning. (5)For example, they can be used to predict faults in design as well as the cost of a design if one is planning to build a road.

在这个段落中，句（1）是主题句，提出计算机在所有领域都有应用的观点；句（2）、（3）和（4）是一级扩展句，都支持和说明句（1），具体说明计算机都在哪些领域应用，而句（5）是二级扩展句，用来补充说明句（4），通过举例来说明计算机辅助设计的用途。

(1)In rock music there is a distinct and almost overwhelming beat. (2)No single beat is

characteristic of the music today. （3）But each song has an easily recognizable rhythm. (4)As you listen to a song, your foot usually starts to pick up the beat. (5)Before long, your entire body seems to be moving with it. （6）Your head pounds with the beat, and there is no room for thought. （7）Only the surge of the music is important. (8)In its own way, rock music is as dominant as the rock Gibraltar. Its message is an overgrowing emotional one.

在这一段中，句（1）是段落主题句，点出本段主题思想，要说明“摇滚乐最突出的特点是其节奏”。句（2）、（3）是一级扩展句，对主题句进一步补充说明；而句（4）、（5）、（6）是二级扩展句，从属于句（2），对句（2）起着补充、解释和说明的作用，更形象、生动地证明了主题句所表达的思想。这里，句（7）是结尾句，它的功用在后面的章节里会做详尽的讲解。

He who mistrusts most should be trusted least.——最不信任别人的人最不应该得到信任。

三、结尾句

结尾句位于段落的末尾，在段落中也起着非常重要的作用，用以对全段内容进行总结、归纳或提出结论性的观点。结尾句常和主题句相呼应，以不同的形式再现主题，并与扩展句相关联。但是并非任何段落都必须有结尾句才算完整。有的段落，尤其是一些较短的段落中只有主题句没有结尾句。

请看下面各段落中结尾句的写法：

Scientists believe that there has been life of some sort on the earth for about twelve hundred million years. Such a large figure is difficult to grasp, so let us scale it down and reckon it as one hundred years. We then find that man has been on the earth for about a month, and civilized man for only seven or eight hours. So you see mankind is only at the beginning of its civilized life, and we must not expect too much.

本段的结尾句是对全段的总结归纳。它进一步强调了段落的中心思想，以引起读者的注意和重视。

A contract is an agreement which is enforceable by law. It can be long or short, formal or informal, simple or complicated, and verbal or written. Without a contract or agreement to bind the contracting parties, any international business or transaction would be impossible. Long age, people exchanged promises in making bargains and binding the conduct of others. This exchange of promises came to be known as “agreement” and became more and more important in the fields of business. A promise or agreement is reached as a result of the process of offer and acceptance.

When an agreement is reached, a cont ract is formed. Once a contract is officially signed by the concerned parties, it creates legal obligations in the sense of law.

本段的最后一句是结尾句，第一句是主题句。结尾句所表达的意思跟主题句一致，但句子结构和用词都不一样。结尾句是主题句的再现，起着前后呼应的作用，段落中心思想更加突出明显。

The alarming problem is the increase in violent incidents owing to love on campus. When failing to win desirable affection from their lovers, some girl students tend to commit suicide while boys turn to knife and poison for revenge. Besides, it is a painful fact that boys obtain money needed for their love in an improper way. To please their girlfriends, boy students always dress smartly, shop generously and eat out frequently; but when finding no other quicker way to make the money needed than by stealing or cheating, they are on the way to imprisonment. Another sensit ive problem is the growing pregnancy rate amon g girl students. The young students are subjected to blame for being too young to put themselves under sensible contr ol, but school authorities cannot escape their share of responsibility.

本段的结尾句提出了结论性观点，既呼应了主题句内容，又与扩展句紧密关联，并且承上启下地引出后面段落的主题。

Eskimos are expert at fishing and hunting. Eskimos know the habits of each animal living in the northern lands. They know that a seal swimming under the ice will keep a breathing hole open by its warm breath, so they will wait beside the hole and kill it. Eskimos fish in the rivers, and when the sea is frozen, they cut holes in the ice and lower fishing lines into the water.

本段没有结尾句。

Idleness is the root of all evils.——懒惰是万恶之源。