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。
�、诋�(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？
③當(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(yuǎn)，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：
①當(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。