关系代词在定语从句中作主语时，从句谓语动词的人称和数要和先行词保持一致 。1)who, whom, that 这些词代替的先行词是人的名词或代词，在从句中所起作用如下： Is he the man who/that wants to see you？他就是你想见的人吗？（who/that在从句中作主语） He is the man whom/ that I saw yesterday.他就是我昨天见的那个人 。
（whom/that在从句中作宾语）2) Whose 用来指人或物，（只用作定语，若指物，它还可以同of which互换），例如： They rushed over to help the man whose car had broken down. 那人车坏了，大家都跑过去帮忙 。Please pass me the book whose (of which) cover is green. 请递给我那本绿皮的书 。
3)which, that 它们所代替的先行词是事物的名词或代词，在从句中可作主语、宾语等，例如： A prosperity which / that had never been seen before appears in the countryside. 农村出现了前所未有的繁荣 。（which / that在句中作宾语） The package (which / that) you are carrying is about to come unwrapped. 你拿的包快散了 。
（which / that在句中作宾语）18.2 关系副词引导的定语从句关系副词可代替的先行词是时间、地点或理由的名词，在从句中作状语 。1)when, where, why 关系副词when, where, why的含义相当于"介词+ which"结构，因此常常和"介词+ which"结构交替使用，例如： There are occasions when (on which) one must yield. 任何人都有不得不屈服的时候 。
Beijing is the place where (in which) I was born. 北京是我的出生地 。Is this the reason why (for which) he refused our offer？ 这就是他拒绝我们帮助他的理由吗？2)that代替关系副词 that可以用于表示时间、地点、方式、理由的名词后取代when, where, why和"介词+ which"引导的定语从句，在口语中that常被省略，例如： His father died the year (that / when / in which) he was born. 他父亲在他出生那年逝世了 。
He is unlikely to find the place (that / where / in which) he lived forty years ago. 他不大可能找到他四十年前居住过的地方 。18.3 判断关系代词与关系副词方法一： 用关系代词，还是关系副词完全取决于从句中的谓语动词 。
及物动词后面无宾语，就必须要求用关系代词；而不及物动词则要求用关系副词 。例如： This is the mountain village where I stayed last year. I'll never forget the days when I worked together with you.判断改错（注：先显示题，再显示答案，横线；用不同的颜色表示 出 。）
（错） This is the mountain village where I visited last year. （错） I will never forget the days when I spent in the countryside. （对） This is the mountain village (which) I visited last year. （对） I'll never forget the days (which) I spent in the countryside.习惯上总把表地点或时间的名词与关系副词 where, when联系在一起 。此两题错在关系词的误用上 。
方法二： 准确判断先行词在定语从句中的成分（主、谓、宾、定、状），也能正确选择出关系代词/关系副词 。例1. Is this museum ___ you visited a few days age? A. where B. that C. on which D. the one例2. Is this the museum ____ the exhibition was held. A. where B. that C. on which D. the one答案：例1 D，例2 A例1变为肯定句： This museum is ___ you visited a few days ago.例2变为肯定句： This is the museum ___ the exhibition was held. 在句1中，所缺部分为宾语，而where, that, on which都不能起到宾语的作用，只有the one既做了主句的表语，又可做从句的宾语，可以省略关系代词，所以应选D 。
而句2中，主、谓、宾俱全，从句部分为句子的状语表地点，既可用副词where，又因 in the museum词组，可用介词in + which 引导地点状语 。而此题中，介词on 用的不对，所以选A 。
关系词的选择依据在从句中所做的成分，先行词在从句中做主、定、宾语时，选择关系代词 （who, whom, that, which, whose）； 先行词在从句中做状语时，应选择关系副词 （ where 地点状语，when 时间状语，why 原因状语）。18.4 限制性和非限制性定语从句1） 定语从句有限制性和非限制性两种 。