十、关系代词
1. 关系代词的用法。主要的关系代词有 that, who, whom, whose, which, as 等。其中who, whom 只用于指人，which, as 只用于指事物，whose, that 既可于指人也可用于指物。关系代词在定语从句主要用于主语、宾语(可以省略)、表语或定语：
He is the man who [that] lives next door. 他就是就是住在隔壁的那个人。
How do you like the photo that [which] I took? 你觉得我拍的这张照片怎么样？
This is the same watch as I lost. 这块表跟我丢失的那块一样。
I want to find someone with whom I could discuss music. 我想找个能和我谈音乐的人。
She received an invitation from her boss, which came as a surprise. 她收到了老板的邀请，这是她意想不到的。
2. that 与 which的用法区别。两者都可指物，常可互换。其区别主要在于：
(1) 引导非限制性定语从句时，通常要用which：
She received an invitation from her boss, which came as a surprise. 她收到了老板的邀请，这是她意想不到的。
(2) 直接放在介词后作宾语时，通常要用which：
The tool with which he is working is called a hammer. 他干活用的那个工具叫做锤子。
(3) 当先行词是下列不定代词或被它们修饰时much, little, none, all, few, every(thing), any(thing), no(thing) 等时，通常用that：
There was little that the enemy could do but surrender. 敌人无法,只有投降了。
All [Everything] that can be done must be done.  凡能做的事都必须做。
(4) 当先行词有the very, the only, the same 等修饰时，通常用that：
This is the only example that I know. 我知道的例子只有这一个。
Those are the very words that he used. 那是他的原话。
(5) 当先行词有形容词最高级或序数词(包括last, next等)等修饰时，通常用that：
This is the best dictionary that I've ever used. 这是我用过的最好的词典。
The first thing that you should do is to work out a plan. 你应该做的第一件事是订个计划。
(6) 当关系代词在定语从句中用作表语时，通常用that：
China is not the country (that) it was. 中国已不是过去的中国了。
(7) 当先行词是一个既指人又指物的并列词组时，通常用that：
They talked about the persons and things that most impressed them. 他们谈论了使他们印象最深的人和事。
(8) 当要避免重复时：
Which is the course that we are to take? 我们选哪门课程？
3. that与who的用法区别。
(1) 两者均可指人，有时可互换：
All that [who] heard him were delighted. 所有听了他讲话的人都很高兴。
Have you met anybody that [who] has been to Paris? 你遇见过到过巴黎的人吗?
He is the only one among us that [who] knows Russian.他是我们中间唯一懂俄语的人。
(2) 但是在下列情况，通常要用 that：
①当先行词是一个既指人又指物的并列词组时：
I made a speech on the men and things that I had seen abroad. 我就我在国外所见到的人和事作了报告。
②当先行词是who时(为避免重复)：
Who was it that won the World Cup in 1982? 谁赢得了1982年的世界杯？
③当关系代词在定语从句中作表语时(可省略)：
Tom is not the boy (that) he was. 汤姆这孩子已不是以前那个样子了。
4. as与which的用法区别
(1) 引导限制性定语从句时，在such, as, the same后只能用as，其他情况用 which：
I never heard such stories as he tells. 我从未听过他讲那样的故事。
It's the same story as I heard yesterday. 这故事跟我昨天听到的一样。
This is the photo which shows my house. 这张照片拍的是我的住宅。
(2) 引导非限制性定语从句时，有时两者可互换：
I live a long way from work, as [which] you know. 我住得离工作单位很远，这你是知道的。
(3) 但在，在以下情况引导非限制性定语从句时，两者不可换用：
① 当从句位于主句前面时，只用 as：
As is known to everybody, the moon travels round the earth once every month. 月球每月绕地球转一周，这是每个人都清楚的。
② as 引导的非限制性定语从句应与主句在意义上和谐一致，which无此限制：
He went abroad, as [which] was expected. 他出国了，这是大家预料到的。
He went abroad, which was unexpected. 他出国了，这让大家感到很意外。(不用as)
③ as 引导非限制性定语从句时，先行词通常不能是主句中某个具体的词，而应是整个句子、整个短语或某个短语推断出来的概念，而which 则无此限制：
The river, which flows through London, is called the Thames. 这条流经伦敦的河叫泰晤士河。(不用as)
④ 当as 引导非限制性定语从句作主语时，其谓语通常应是连系动词，而不宜是其他动词，而 which则无此限制：
She has married again, as [which] seemed natural. 她又结婚了，这似乎很自常。
She has married again, which delighted us. 她又结婚了，这使我们很高兴。(不用as)
5. who与whom的用法区别。两者均只用于人，从理论上说，who 为主格，whom为宾格：
Where's the girl who sells the tickets? 卖票的女孩在哪里？
The author whom you criticized in your view has written a letter in reply. 你在评论中批评的那个作者已写了一封回信。
但实际上，除非在正式文体中，宾格关系代词 whom 往往省略不用，或用who或that代之：
The man (that, who, whom) you met just now is called Jim. 你刚遇见的那个人叫吉姆。
不过，在以下几种情况值得注意：
(1) 直接跟在介词后面作宾语时，只能用 whom，而且不能省略：
She brought with her three friends, none of whom I had ever met before. 她带了3个朋友来，我以前都没见过。
(2) 引导非限制性定语从句且作宾语时，who 和 whom均可用，但以用 whom 为佳，此时也不能省略：
This is Jack, who [whom] you haven't met before. 这是杰克，你以前没见过。