which在定语从句中的用法

1.首先关系代词which在定语从句指物，在定语从句中作主语、宾语或定语，既可引导限制性定语从句，又可引导非限制性定语从句。

1. 1. 引导限制性定语从句
E.g: A shop should keep a stock of those goods wh ich sell best. 商店应存有最畅销的货物。

1.2. 引导非限制性定语从句。

（ 1 ）用来指代一个句子。

E.g:Internet is so interesting, which makes all poss ible happen. 因特网是如此有趣，它使任何事都有可能发生。

（ 2 ）用来指代句子的一部分。

E.g:When deep in thought, which he often was, he w ould forget all around him.
他常常陷入沉思，这时他就会忘掉周围的一切。

（ 3 ）如果要引导两个非限制性定语从句，第二个which 前要加and.
E.g:He bought a book, which was written by Lu Xun, and which he decided to give to his friend.
他买了本鲁迅写的书，他决定送给朋友。

2.which和that在定语从句中的区别
2.1使用that的情况：
1）当先行词是nothing, something, anything, all, each等不定代词时。

E.g: Do you have anything that is important to tell me?
2）当先行词被all, any, some, no, not, every, each等修饰时。

E.g: I have some books that are very good.
3）当先行词被形容词最高级、序数词所修饰时。

E.g:This is the first book that I bought myself.
The biggest bird that I caught is this bird.
4）主句是以which或who开头的特殊疑问句时
E.g: Which is the bike that you lost?
Who is the woman that was praised at the meeting.
5)当先行词在从句和主句中都作表语时,无论先行词是人还是物.
E.g:China is no longer the country that she was.
6）如有两个定语从句,其中一个已用which引导,另一个宜用that .
E.g:Edison built up a factory which produced things that had never been seen before.
7）在there be句型中,只用that.
E.g：He asked for the latest book (that) there is on the subject.
8)当先行词被the very, the last, the next, the only 等词修饰时。

E.g： This is the very book that I lost yesterday.
9)当先行词又有人又有物时。

E.g： I won’t forget the things and the persons that I saw.
2.2 只能使用which的情况：
1)非限制性定语从句中。

E.g： Mary has a book, which is very precious.
2)在介词之后。

E.g:This is a house in which lives an old man.
3)当主句中的主语被that修饰时。

E.g: That dog which I found in the street belongs to Mary.
3.定语从句中as和which的区别
3.1 as引导的定语从句表示说话人对话语的看法、态度、依据、解释或评论。

具有下列特点：
1）as用于引导定语从句时，具有“正如……、像……、由……而知”等语义。

如：
E.g:He was strongly against the plan，as could be expected．正如所料，他强烈反对这项计划。

2）as引导的定语从句在语义上要和主句保持一致，而which可不一定，如果语义不一致，则要用which来替代as。

如：
E.g:He married again，as（which）was natural．
他又结婚了，这是自然的。

3）as引导的定语从句，其先行词可由以下词来修饰，the same ／such ／as等。

也可以由which来改写，但不可直接替换。

E.g:This is the same sum as was spent in that year on private
motoring．＝This is the sum which was spent in that year on private motoring．
这与那年用于私人汽车所花的费用相同。

4)as引导的非限制性定语从句可放在主句之后，也可放在主句之前。

但which只能放在主句之后。

如：
E.g:As we have seen，oceans cover more than 70％of the earth．如我们所见，海洋覆盖地球70％多的面积。

E.g:He seemed a foreigner，which in fact he was．
他看上去像个外国人，事实上他就是。

5)as在定语从句中作宾语时，从句的谓语动词常是see ／watch ／know ／hear等表示感知的动词，且谓语动词前带有情态动词can ／could ／may等，此外常用的动词还有say ／tell ／remember等。

E.g:It was true，as everybody could know．
这是真的，大家都知道。

6)as在定语从句中作主语时，其谓语动词可以是及物动词的被动语态，也可以是be或其它连系动词。

如是不及物动词，则不存在以上关系。

可以说as often hap- pens（appears）等。

E.g；He came back yesterday，as was expected．
他如期昨日返回。

3.2 which引导的此类从句，是对主句所叙述的事情进行补充说明，表明事物的状态或结果。

一般有下列特点：
1）如果定语从句的谓语是行为动词的主动语态，且关系代词在从句
中作主语时，一般要用which，这时which可以用 and that改写为并列句。

E.g:Things then greatly changed，which surprised us．＝Things then greatly changed，and that surprised us．
那时事情巨变，使我们惊讶。

2)由“介词＋关系代词”引导的关系分句多用于正式文体中，常用“介词＋ which”，不用“介词＋as”。

E.g:They tried to think of a plan by which they could finish their task ahead of time．
他们试图想个计划，以便提前完成任务。

3.3 在与上述几条不冲突的情况下，as和which可以换用。

E.g:A horse is a useful animal，as ／which everybody knows．众所周知，马是有用的动物。