關(guān)系代詞的概念：
英語中的關(guān)系代詞有who, whom, whose, that, which, 它們是用來引導(dǎo)定語從句的。關(guān)系代詞既代表定語從句所修飾的詞，又在其所引導(dǎo)的從句中承擔(dān)一個成分，如主語、賓語、表語、或定語。
如：This is the man who saved your son. (who在從句中作主語，先行詞是man）
The man whom I met yesterday is Jim.
A child whose parents are dead is an orphan.
He wants a room whose window looks out over the sea.
關(guān)系代詞用法：
1、that與which的用法區(qū)別：
兩者都可指物，�？苫Q。其區(qū)別主要在于：
（1）引導(dǎo)非限制性定語從句時，通常要用which：
如：She received an invitation from her boss, which came as a surprise. 她收到了老板的邀請，這是她意想不到的。
�。�2）直接放在介詞后作賓語時，通常要用which：
如：The tool with which he is working is called a hammer. 他干活用的那個工具叫做錘子。
�。�3）當(dāng)先行詞是下列不定代詞或被它們修飾時much, little, none, all, few, every(thing), any(thing), no(thing)等時，通常用that：
如：There was little that the enemy could do but surrender. 敵人無法,只有投降了。
All[Everything] that can be done must be done. 凡能做的事都必須做。
（4）當(dāng)先行詞有the very, the only, the same等修飾時，通常用that：
如：This is the only example that I know. 我知道的例子只有這一個。
Those are the very words that he used. 那是他的原話。
（5）當(dāng)先行詞有形容詞最高級或序數(shù)詞（包括last, next等）等修飾時，通常用that：
如：This is the best dictionary that I've ever used. 這是我用過的最好的詞典。
The first thing that you should do is to work out a plan. 你應(yīng)該做的第一件事是訂個計劃。
（6）當(dāng)關(guān)系代詞在定語從句中用作表語時，通常用that：
如：China is not the country(that) it was. 中國已不是過去的中國了。
�。�7）當(dāng)先行詞是一個既指人又指物的并列詞組時，通常用that：
如：They talked about the persons and things that most impressed them. 他們談?wù)摿耸顾麄冇∠笞钌畹娜撕褪隆?/p>
（8）當(dāng)要避免重復(fù)時：
如：Which is the course that we are to take? 我們選哪門課程？
2、that與who的用法區(qū)別：
（1）兩者均可指人，有時可互換：
如：All that[who] heard him were delighted. 所有聽了他講話的人都很高興。
Have you met anybody that[who] has been to Paris? 你遇見過到過巴黎的人嗎?
He is the only one among us that[who] knows Russian. 他是我們中間唯一懂俄語的人。
�。�2）但是在下列情況，通常要用that：
�、佼�(dāng)先行詞是一個既指人又指物的并列詞組時：
如：I made a speech on the men and things that I had seen abroad. 我就我在國外所見到的人和事作了報告。
②當(dāng)先行詞是who時(為避免重復(fù))：
如：Who was it that won the World Cup in1982? 誰贏得了1982年的世界杯？
�、郛�(dāng)關(guān)系代詞在定語從句中作表語時(可省略)：
如：Tom is not the boy(that) he was. 湯姆這孩子已不是以前那個樣子了。
關(guān)系代詞知識體系：
關(guān)系代詞用法拓展：
1、as與which的用法區(qū)別：
(1)引導(dǎo)限制性定語從句時，在such,as,thesame后只能用as，其他情況用which：
如：I never heard such stories as he tells. 我從未聽過他講那樣的故事。
It's the same story as I heard yesterday. 這故事跟我昨天聽到的一樣。
This is the photo which shows my house. 這張照片拍的是我的住宅。
(2)引導(dǎo)非限制性定語從句時，有時兩者可互換：
如：I live a long way from work, as [which] you know. 我住得離工作單位很遠，這你是知道的。
(3)但在，在以下情況引導(dǎo)非限制性定語從句時，兩者不可換用：
�、佼�(dāng)從句位于主句前面時，只用as：
如：As is known to everybody, the moon travels round the earth once every month. 月球每月繞地球轉(zhuǎn)一周，這是每個人都清楚的。
�、赼s引導(dǎo)的非限制性定語從句應(yīng)與主句在意義上和諧一致，which無此限制：
如：He went abroad, as[which] was expected. 他出國了，這是大家預(yù)料到的。
He went abroad, which was unexpected. 他出國了，這讓大家感到很意外。(不用as)
�、踑s引導(dǎo)非限制性定語從句時，先行詞通常不能是主句中某個具體的詞，而應(yīng)是整個句子、整個短語或某個短語推斷出來的概念，而which則無此限制：
如：The river, which flows through London, is called the Thames. 這條流經(jīng)倫敦的河叫泰晤士河。(不用as)
�、墚�(dāng)as引導(dǎo)非限制性定語從句作主語時，其謂語通常應(yīng)是連系動詞，而不宜是其他動詞，而which則無此限制：
如：She has married again, as[which] seemed natural. 她又結(jié)婚了，這似乎很自常。
She has married again, which delighted us.她又結(jié)婚了，這使我們很高興。(不用as)
2、who與whom的用法區(qū)別：
兩者均只用于人，從理論上說，who為主格，whom為賓格：
如：Where's the girl who sells the tickets? 賣票的女孩在哪里？
The author whom you criticized in your view has written a letter in reply. 你在評論中批評的那個作者已寫了一封回信。
但實際上，除非在正式文體中，賓格關(guān)系代詞whom往往省略不用，或用who或that代之：
如：The man(that, who, whom) you met just now is called Jim. 你剛遇見的那個人叫吉姆。
不過，在以下幾種情況值得注意：
(1)直接跟在介詞后面作賓語時，只能用whom，而且不能省略：
如：She brought with her three friends, none of whom I had ever met before. 她帶了3個朋友來，我以前都沒見過。
(2)引導(dǎo)非限制性定語從句且作賓語時，who和whom均可用，但以用whom為佳，此時也不能省略：
如：This is Jack, who[whom] you haven't met before. 這是杰克，你以前沒見過。