what在定语从句中为什么不能用

what在定语从句中为什么不能用？你知道原因吗？以下是小编整理的相关语法，欢迎阅读。

定语从句概念：

在复合句中作定语的从句叫做定语从句。定语从句修饰的词叫做先行词，引导定语从句的词叫做关系词。关系词分为关系代词和关系副词。关系代词有：that，which，whom，whose，其中that，which，who在定语从句中做主语、宾语或表语，whom做宾语，whose做定语。

　　what在定语从句中为什么不能用？

what 一般不能用于引导定语从句,what就相当于先行词加关系代词that或which.特殊情况下,what也可以引导定语从句一般只用来引导名词性从句（主语从句、宾语从句、表语从句和同位语从句）.

定语从句的引导词为which,that,when,where,why总之，What不可以引导定语从句。它只可以引导名词性从句,在句中相当于 what =all that ,what 在名词性从句中充当成分，常常作主语、宾语和表语。

定语从句如何用？

定语从句（Attributive Clauses）在句中做定语,修饰一个名词或代词,被修饰的名词,词组或代词即先行词.定语从句通常出现在先行词之后,由关系词（关系代词或关系副词）引出.

关系代词有：who,whom,whose,that,which等.

关系副词有：when,where,why等.18.1 关系代词引导的定语从句

关系代词所代替的先行词是人或物的名词或代词,并在句中充当主语、宾语、定语等成分.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.