一、关系词的用法特点关系词分关系代词和关系副词。关系代词主要有 that, who, whom, whose, which, as 等，其中who等，其中whowhom 只用于指人，which和as 只用于指事物，whose和 that既可于指人也可用于指物，它们在定语从句可用作主语、宾语、表语或定语；关系副词主要有when, where 和why，其中when表示时间，whenwhere表地点，why表原因，它们在定语从句中均用作状语：The dog which [that] was lost has been found. 丢失的狗找到了。(which / that指物，在从句中用作主语)I have forgotten everything that I learnt at school. 我把学校学的所有东西都给忘了。(that指物，在从句中句作宾语(that)The man who lives in that house is my uncle. 住在那座房子里的人是我叔叔。(who指人，在从句中作主语)It was an island whose name I have forgotten. 这是一座岛，名字我忘了。There are some students whose questions I can’t answer. 有些学生提出的问题我回答不了。(whose指人，在从句中作定语)

　　二、关系词的选择选择关系词可考虑以下四点：(1) 一看先行词的意义，即分清先行词是指人、指物、时间、地点还是原因(如指物时不能用who或whowhom，指人时通常不用which等)。(2) 二看关系词的句法功能，即分清关系词是担任什么句子成分，是作主语还是宾语、是作定语还是状语等(如作定语通常用whose，有时也用which；作状语要用when, where, why)；作状语要。(3) 三看定语从句的种类，即分清是限制性定语从句还是非限制性定语从句(如that和why通常不引导非限制性定语从句)。(4) 四看文体，即分清是正式文体还是非正式文体，是书面语体还是口语体。(4)

　　三、两组关系词的用法区别1. that 与 which的用法区别两者都可指物，有时可互换。其区别主要在于：(1) 引导非限制性定语从句时，通常只用which：He drove too fast, which was dangerous. 他开车很快，这是很危险的。(2) 直接放在介词后作宾语时，通常只用which： whichThe 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much, little, none, all, few, every(thing), any(thing), no(thing) 等不定代词或受其修饰时，通常用that：All [Everything] that can be done must be done. 凡能做的事都必须做。(4) 当先行词受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. 中国已不是过去的样子了。(7) 当先行词是一个既指人又指物的并列词组时，通常用(7) 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?2. 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. 他是我们中间惟一懂俄语的人。(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 that has sympathy can laugh on that occasion? 有同情心的人谁会在那个时候发笑呢?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。