大学定语从句
定语从句是在句中起形容词作用的句子，通常修饰它前面的名词或代词。
重点要求：
1．限制性定语从句和非限制性定语从句区别和结构特点。
2．关系代词who, which, that, whose，whom引导定语从句时的使用特点。
3．关系副词when, where, why 引导定语从句时的使用特点。
4．as引导定语从句的使用。
定语从句在句中起定语作用，修饰某一名词或代词。定语从句所修饰的词叫先行词，定语从句放在先行词后面。引导定语从句的关系代词，指人的有who、whom、that、whose，指物的有which、that、whose。
定语从句分为两类：限制性定语从句和非限制性定语从句。
限制性定语从句是主句中的先行词不可缺少的定语，不可用逗号分开。
非限制性定语从句只对主句中的先行词作附加说明，关系不密切，主句与从句之间用逗号分开，不能用that连接。例：
I have a sister who works in a bank.限制性定语从句（我有一个在银行工作的姐姐。）
I have a sister, who works in a bank.非限制性定语从句（我有一个姐姐，在银行工作。）
关系代词whose在定语从句中作定语。例：Edison is a great inventor (whose) fame is world-wide.
关系代词that和which都可以指物，但先行词为不定代词以及先行词被序数词或最高级形容词修饰时用that。
引导定语从句的关系副词有when、where、why。例：
The day (when) I helped the old man out was a very happy one for me.
The reason (why) the gamblers lose in the end is that they are dishonest.
关系副词的先行词总是表示时间、地点或理由的名词。
As引导的定语从句
(1) as用作关系代词和关系副词引导限制性定语从句，并在从句中作定语、表语或状语，构成the same…as，such…as等结构。例：I like the same book as you do.I want to do it in the same way as you did.
(2) as引导非限制性定语从句。as在定语从句中作主语，表语或宾语，这个定语从句说明整个句子，它可以放在主句之前。例：As is known to all, he is the best student in our class.
1、关系代词在从句中作主语时,从句的'谓语动词的人称和数必须和先行词保持一致.
2、关系代词whom, which, that 在限制性定语从句中作动词宾语或介词宾语,而该介词又位于从句末尾时,经常省略，但as一般不省略.
3、关系代词which在非限制性定语从句中不能放在句首，as既能在句首也能在句中。
4、that在定语从句中可以指人或物，在从句中作主语或谓语动词的宾语，但不能放在介词后面作介词宾语。
5、先行词表示地点时，有时用where，有时用that，which来引导定语从句，这时要根据从句的谓语动词是及物还是不及物，是及物的就用that(which)，否则用 where。
例：This is the factory where we worked last is the factory that (which) we visited.
that与which都做定语从句的关系代词，其用法有如下区别：
1．先行词是不定代词：all，few，little，much，something，nothing，anything等，只能用that。例：That’s all (that) I want to say. 这就是我想要说的。
2．先行词被序数词或形容词最高级所修饰，只能用that。例：This is the most exciting film (that) I have ever seen. 这是我看过的最动人的电影。
3．先行词被the only，the very，the same，the last修饰时，只能用that。例：He is the only person that attended the meeting. 他是唯一参加那个会议的人。
4．that在定语从句中可以指人或物，而which只能指物。例：
The letter that/which I received was from my father. 我收到的信是我父亲写的。
The girl that was playing basketball was my younger sister.打篮球的那个女孩是我妹妹。
5．先行词是moment，time，way，speed等词时用that，此时其在从句中起状语作用。例：It was the first time that (= when) Mark had been late for class. 这是马克第一次上课迟到。
6．先行词中既有人又有物，只能用that。例：The people and supplies that belongs to Company 9 should come to bridge before 9 p.m. 九连的人员和装备应该在晚上9点以前到达大桥。
7．非限定性定语从句关系代词用which，而不用that。例：The basketball, which was bought last week, was leaking air. 上周买的那个篮球漏气了。
8．在引导非限定性定语从句时，which还可以代表前面整个句子或其部分意思。例：He has to work on Sundays, which is bitter for him. 他不得不在周日工作，这是令他痛苦的事。
9．在关系代词前使用介词时只能用which，不能用that。例：The train on which she was traveling was late. 她所乘坐的火车晚点了。
