职称英语理工类语法词汇常见考点：复合句

　　B. 复合句：

　　复合句是由主句+从句构成，它是英语学习中比较复杂的句子结构。一般来说，英语中一个句子只能有一个谓语，如果出现两个谓语，那么其中一个谓语只能是以从句的形式或并列句或非谓语动词的形式出现。所谓从句是指从属于主句的句子，由从属连词连接。从句的种类有很多，但根据其性质和作用可以分为：名词性从句，形容词性从句，副词性从句三大类。

　　a. 定语从句这是出现在阅读题型中最多的从句!重要!

　　定语从句：在句中做定语，修饰一个名词或代词。

　　先行词：被定语从句修饰的名词,词组或代词。

　　关系词：引导定语从句的词;一般紧跟在先行词后引出定语从句。分为关系代词和关系副词。

　　关系代词有：who, whom, whose, that, which等。

　　关系副词有：when, where, why等。

　　关系词常有3个作用：1，引导定语从句。2，代替先行词。3，在定语从句中担当一个成分。

　　例如:

　　Once upon a time, there was a king .

　　先行词 关系词

　　For one thing, the tigers were often used in court.

　　先行词 关系词

　　There came out a young lady .

　　先行词 关系词

　　They would meet on the night .

　　关系代词引导的定语从句

　　关系代词在定语从句中作主语时，从句谓语动词的人称和数要和先行词保持一致。

　　 A teacher is a person who passes knowledge to the student.

　　 The book that is on the desk was written by Yao Ming.

　　2. 关系代词在定语从句中作宾语时，可以省略。

　　 Behind one door was a hungry tiger the guards had put there.

　　 The tiger would immediately jump upon the poor man the guards had brought to the arena.

　　3. whose只用作定语,可以用来指人或物; 若指物，它还可以同of which互换, 例如：

　　 They rushed over to help the man whose car had broken down.

　　 Please pass me the book whose cover is green.

　　关系副词引导的定语从句

　　关系副词可代替的先行词是时间、地点或理由的名词，在从句中作状语。

　　1. 关系副词when, where, why的含义相当于介词+ which结构，因此常常和介词+ which 结构交替使用，例如：

　　There are occasions when one must yield.

　　Beijing is the place where I was born.

　　Is this the reason why he refused our offer?

　　限制性和非限制性定语从句

　　例如：

　　1)This is the house which we bought last month.

　　The house, which we bought last month, is very nice.。

　　2) 当先行词是专有名词或物主代词和指示代词所修饰时，其后的定语从句通常是非限制性的，例如：

　　Charles Smith, who was my former teacher, retired last year.

　　My house, which I bought last year, has got a lovely garden.

　　This novel, which I have read three times, is very touching.

　　3) 非限制性定语从句还能将整个主句作为先行词, 对其进行修饰, 这时从句谓语动词要用第三人称单数，例如：

　　He seems not to have grasped what I meant, which greatly upsets me.

　　Liquid water changes to vapor, which is called evaporation.

　　说明：关系代词that和关系副词why不能引导非限制性定语从句。