关系代词的使用在句子中功能相当于形容词短语用作名词定语的从句称为定语从句定语从句所 修饰的名词叫做先行词，定语从句通常紧跟其后定语从句可由关系代词引导关系代词常见者有：who, whom, whose, which, that等，其使用取决于先行词是人还是物，还取决于关系代词在句中作何句子 成分一、先行词表人时关系代词的使用：1. 在从句中用作主语时一用who或that (其谓语动词的人称和数与先行词一 致)如：He is the person who/that is going to give a concert on the century square. 他就是那个要在世纪广场举行音乐会的人They are the people who/that are going to give a concert on the century square. 他们就是那些要在世纪广场举行音乐会的人在从句中用作主语时可省略关系代词的特殊情况：简单句：The boy is my brother. The boy is standing at the door.合并：The boy who is st anding at the door ismy brother.The boy standing at the door is my brother.首先找出这个句子的主干。
The boy is my brother.然后把修饰词加入站在门边的男孩是我兄弟 “st anding at the door ”是修饰bo y的，放在boy后面如果动词就是修饰前面的人或物的话，那么关系代词就可以省略比 如这里，standing at the door就是修饰boy的，所以who is就可以省略了2. 在从句中用作表语时一通常用which，常省略如：She decided that she would be the writer (which) her mother wan ted her to be. 她决定要成为她母亲想要她成为的那种作家3. 在从句中用作动词宾语时一用who(m)或that，口语中皆可省略如：I teleph oned the doctor (who/whom/that) Jacks on had recomme nded.我给杰克逊推荐的那个大夫打了4. 在从句中用作介词宾语时一介词在关系代词前时用whom；介词在句末时用 who(m )或that，口语中此时皆可省略如：He is not the young scientist to whom I referred.He is not the young scientist (who/whom/that) I referred to.他不是我说的那个年轻科学家5. 在从句中用作名词的定语时一用whose。
如：I have never yet met a woman whose figure is so beautiful.我从未见过体型这么美的妇女二、先行词表物时关系代词的使用：1. 在从句中用作主语时一用that或which (其谓语动词的人称和数与先行词一 致)如：It is a problem that/which needs very careful consideration.这是一个需要非常认真考虑的问题These are problems that/which need very careful consideration. 这是一些需要非常认真考虑的问题2. 在从句中用作表语时一通常用which，常省略如：The typewriter is not the machine (which) it was.这打字机已不是原来的样子了3. 在从句中用作动词宾语时一用that或which， 口语中皆可省略如：I'm using the same computer (that/which) I have used for four years.我在用那台已经用了四年的计算机4•在从句中用作介词宾语时一介词在关系代词前时用which；介词在句末时用w hich或that，口语中此时皆可省略。
如:I have problems of my own of which you know nothing.I have problems of my own (that/which) you know nothing of.我有你毫不了解的我自己的问题5•在从句中用作名词的定语时一用whose或of which(用于正式语体中)在实际 语言中，通常用其他手段代替如：Have you seen the machine whose parts are small?Have you seen the machine the parts of which are small?你见过那台零件小的机器吗？在下列几种情况下，关系代词通常用that1. 先行词为 all, anything, everything, nothing, much, none, little 等非人称不定代词时 如：I have n ever take n anything that does n't bel ong to me.我从未拿过不属于我的任何东西2. 先行词有形容词最高级形式修饰时如：He was one of the greatest scientists that ever lived.他是有史以来最伟大的科学家之一。
3. 先行词有first, last, next, only等修饰语时如：The only thing (that) he did was to call the police.他做的唯一的一件事是报警。