4.1 句子的分类（The classification of sentences）

4.1.1 按结构分（By structure）：以从句的类型和数量进行分类；

• 单句（Simple sentences): 一个简单的句子，没有从句，如：

A simple sentence goes like this.

• 并列复合句（Compound sentences）：以并列连词连接多个相对独立的简单句构成，如：

He is handsome and the princess is willing to marry him.

• 从属复合句（Complex sentences）：以从属连词或副词连接的一个主句和至少一个从句构成，如：

He is the man who I saw in the park yesterday.

• 并列从属复合句（Compound-complex sentences）：由多个独立主句及至少一个从句构成，如：

He called the security guard and he checked the room for items which have been stolen.

4.1.2 按作用分（By purpose）：

• 陈述句（Declarative sentences）：以陈述为主，如：

I have to go to work.

• 疑问句（Interrogative sentences）：以提问为主，如：

Do I have to go to work?

• 感叹句（Exclamatory sentences）：以强调或表达特殊的感情为主，如：

I have to go to work!

• 祈使句（Imperative sentences）：告诉、命令或指使某人做某事，如：

Go to work!

• 指导句（Instructive sentences）：提供信息以指导或启发是什么或怎么做，如：

Sentence length, as well as word difficulty, are both factors in the readability of a sentence.

4.2 并列复合句（Compound sentence）

• 用并列连词连接多个简单句组成的句子。
• 常见并列连词： and, or, nor, yet, but, for, so 及复合连词and so, and yet等，如

He is handsome and the princess is willing to marry him.
The city is not beautiful, nor it is clean.
I like action movies, but she doesn't like them.
Take the chance, or you will regret.
I'd better take an umbrella, for it is going to rain.
I don't eat much, (and) yet I am a size 16...
People are living longer than ever before, (and) so even people who are 65 or 70 have a surprising amount of time left...

• 注意：

  • 非并列连词：before, after, because等均不能构成并列复合句，如

  Try to finish your work before you leave.

  • 常见伪连词：therefore, however, moreover / furthermore, nonetheless / nevertheless, notwithstanding, then.

  错误范例：
  This was not an easy decision, however, It is a decision that we feel is dictated by our duty.

  正确范例：
  This was not an easy decision. However, it is a decision that we feel is dictated by our duty.
  This was not an easy decision; However, it is a decision that we feel is dictated by our duty.
  This was not an easy decision. It is, however, a decision that we feel is dictated by our duty.
  This was not an easy decision. It is a decision that we feel is dictated by our duty, however.

4.3 从属复合句（Complex sentence）

从属复合句句（complex sentence），也称从句、主从复合句，用代词、副词和连词把一个简单句作为另外一个简单句的从属成分的句子。所以区分复合句和复杂句的关键就在中间的引导词上。

从属复合句 = 主句 + 引导词 + 从句 （+引导词 + 从句）...

如：The boy, who is crying as if his heart would break, said when I spoke to him, that he was very hungry because he had had no food for two days.

4.3.1 名词性从句：

包括主语从句、宾语从句、表语从句和同位语从句。

• 以that/whether/if做引导词加完整句子构成从句：

That you are right is a lie.
I don't know whether he is trustworthy.
I believe (that) you are right. (连词that引导宾语从句，只起连接主、从句的作用，它本身无意义，在口语或非正式文体中常省略。)

• 以特殊疑问句的陈述语序作为从句:

What he wants to tell us is not clear.
It is still unclear which team will win the match.
I hate it when they speak with their mouths full of food. (it是形式宾语，当不定式（短语）、动名词（短语）或从句在某个句子中作宾语时，为保持句子结构平衡，避免句式结构的混乱，常用it作形式宾语，而将真正的宾语放在句尾。)
It is known to us how he became a writer.

• 同位语从句 = 抽象名词 + 引导词 + 同位句 抽象名词：先行词通常为抽象概念，如fact / idea / news / information / order / belief / advice / suggestion等：

The idea that you can do this work well without thinking is quite wrong.
The thought came to him that maybe the enemy had fled the city.
I have no idea what size she wears.

4.2.2 形容词性从句：定语从句

• 关系代词that/which/who/whom/whose + 不完整句子，如：

He is the man whom I saw yesterday.
They rushed over to help the man whose car had broken down.

• 关系副词when/where/why + 完整句子，如：

There are occasions when one must yield.
Is this the reason why he refused our offer?
Wuhan is the place where I was born.

4.2.3 副词性从句：状语从句

• 时间：当…的时候：when，while，如：

When the dry desert ends, the green grass grows.

在…之前/之后：before，after，如：

Before I arrived, she had come.

一…就…：as soon as

• 地点，如：

Where there is a will, there is a way.

• 原因：because / as / since / for这几个都是表示原因理由的连词，但在用法上各不相同。在份量上，because 语气最强，其次是 since ，再次是as，至于for，则并不成其为原因，至多只是一种理由而已。如：

I am not able to begin the work at once, for I am about to start on a journey.

• 目的：so that和in order that，如：

Such a plan should be carried out so that the goal of education could be better met.

• 结果：So…that和such…that，如：

This is such an important meeting that you should attend it.（=This is so important a meeting that you should attend it.）

• 条件：if/unless/as long as，分别表示如果/除非/只要，如：

If the economy still develops at present way, the environment will be getting worse and worse. Unless it mentioned,

• 让步：尽管/虽然though/although，即使even if/even though（前者是未发生，后者是已发生），无论wherever/whenever，如：

Although advertisements are never without disadvantages, their advantages carry more weight.

• 比较：as…as…/not so…as…/than/the…the…，如：

The more we study, the better we understand life.