定语从句中什么时候用that什么时候用who.which
引导状语从句的连词as可以用作关系代词，引导定语从句，因而被称作准关系代词。
1. 准关系代词as引导限制定语从句，用于以下3个结构中，as在从句中作主语、宾语或表语：
a. so / such…as
Such people as were mentioned by him were honest. (as作主语)
I’ve never seen such a clever man as he is. (as作表语)
Last term our maths teacher set so difficult an (= such a difficult) examination problem as none of us worked out.
b. the same…as
Modern statemen are often faced with the same problem as defeated the ancient Romans. (as 作宾语)
I like the same book as you do. (as 作宾语)
c. as…as
As many children as came were given some cakes. (as 作主语)
He is as diligent a man as ever lived. (as 作主语)
补充：
a. such…as 与 such…that的区别
such…as 引导定语从句；such…that引导结果状语从句。
They talked in such simple English as children could understand.
他们用孩子们能听懂的简单的英语交谈。
They talked in such simple English that children could understand it.
他们用十分简单的英语交谈，连孩子们都能听懂。
I will provide you with such things as you may need.
我要供给你一些你可以用得着的东西。
He shut the window with such a force that the glass broke.
他如此用力地关门，结果玻璃碎了。
b. the same…as与the same…that的区别：
the same…as指两物相似，the same..描述的是同一物。
This is the same bag as I lost yesterday.
这个书包和我昨天丢失的（书包）相似。（相似物）
This is the same bag that I lost yesterday.
这正是我昨天丢失的那个书包。（同一物）
2. 准关系代词as引导非限制定语从句。
a. as引导非限制性定语从句，只代表主语或主句的一部分所表达的意思(不能指代某个名词或代词)，可以放在主句前，后或中间，在从句中作主语或宾语、例如：
As is known to all, he is the best student in our class. (as指代整个句子，作主语，置于句首)
He opposed the idea, as could be expected. (as 指代整个句子，作主语，置于句末)
As we all know, he studies very hard. (as 指代整个句子，作宾语，置于句首)
Taiwan is, as you know, an inseparable part of China. (as指代整个句子，作宾语，置于句中)
常用的这类句式有：
as is said above 综上所述 - as is known to all 众所周知
as is often the case 通常如此 - as is reported in the newspaper 如报纸所报导的
b. 主句具有否定意义，as引导的定语从句位于主句之后时，as指代得主句不包括否定意义，并可用but取代。例如：
Whales are now fish, as some people think / but some people think they are.
I am no orator, as Brutus is.我不善言词,而勃鲁特斯却是个雄辩家.
Spiders are notinsects,as many people think, nor even near1y related to them.
蜘蛛不是昆虫,尽管许多人认为它是昆虫,它甚至与昆虫几乎没有关系.
但as引导的定语从句谓语主句前时，as指代的主句仍包括否定意义。
As has been said above, grammar is not a set of dead rules.
正如前面所说的，语法不是一套死条纹。
3. 在非限制性定语从句中，which和as引导定语从句时的区别：
a. which引导的从句不能放在主句前，而as引导的从句则既可以放在主句前，也可以放在主句后。
b. 用能做关系代词，as和which都可以指代一个句子，但as有“正如”、“就像”之意，which则没有此含义。
He is a foreigner, as I know from his accent. (as指代一个句子，意为“正如”、“就像”)
He has to work on Sunday, which he doesn’t like. (which指代一个句子，没有“正如”、“就像”)
c. 当从句的谓语动词是be或相当于联系动词的seem, become等时，可用as或which作主语。但当从句的谓语是行为动词时，只能用which作主语。
4. as 可用作连词，引导状语从句，构成省略形式“as + 过去分词”这一特殊结构，译成汉语时作用如定语。例如：
The bridge as shown in the picture is really wonderful. (as shown = as it is shown 可译为“图中的桥”)
See the answers as given at the end of this book. (as given = as it is shown 可译为“书后给出的答案”)
English as spoken is Australia is slightly different from British English.
(as spoken = as it is spoken 可译为“在澳大利亚讲得英语”)
请看下列的“as + 过去分词”结构用于修饰前面的名词：
The study as described in the article… 如文章中描述的那种学习
The program as conducted by… 由…指挥的（指导的）节目
The art as applied to medicine… 应用于医学的艺术
The products as seen on TV…电视上看到得产品
首先你应该明确的是 when where在定于从句中是关系副词，而which who that则是关系代词。关系副词引导的从句中不应该缺少句子成分e.g:That is a time when I played happily with my friends.
从句：I played happily with my friends中主语是I，谓语是play，宾语是my friends。不缺少成分，又因为先行词是time，所以连接此为when.耳由关系代词连接的定语从句中是缺少句子成分的。e.g: The man who is wearing a hat is our class teacher.从句：who is wearing a hat is our class teacher中只有谓语和宾语，没有主语，故用who.
但是who which that只见又有少许区别who修饰人、which修饰物、that修饰人、物皆可。
1、that的用法
that的先行词是人或物,在定语从句中作主语、宾语或表语。
主要特点有：
①that在定语从句中作主语时不省略,作宾语时可以省略；
②that不引导非限制性定语从句；
③that前不加介词
例子Theforeigners that visited our school yesterday are from Canada.
昨天参观我们学校的外国人来自加拿大。(that代替人作主语)
只能用that引导定语从句的情况:
①先行词被序数词或形容词最高级修饰；
②先行词是不定代词all, the one, everything等；
③先行词被 any , the only , the last等修饰；
④先行词既指人又指物时。
例子Alice is the only person ( that ) I can trustin the office.
爱丽丝是办公室里我唯一信任的人。(先行词被the only修饰只用that)
2、which的用法
先行词是物,在定语从句中作主主语或宾语。
主要特点：
①which在定语从句中作主语时不能省略,作宾语时可以省略,引导非限制性定语从句时不能省略；
②which的前面可以有介词;
③which的先行词可以是前面数个的的句子,意为”这使…….;这一点……”。
例子 A computeris a machine which can do many things for us.
电脑是一种可以为我们做许多事情的机器。( which作主语)
3、who的用法
who的先行词是人。who在定语从句中作主语、宾语或表语。
例子 I like theboy who gets along well with his classmates
我喜欢那个与他的同学相处得好的男孩。
先行词为one、ones、anyone或 those时,或双重定语从句中一个定语从句的关系代词是that，另一个指人的关系代词词用who。
扩展资料
在定语从句中which和that用法区别：在定语从句中，which 和that 在指代事物时，一般可以互换使用，但并非在任何情况下都是这样，几种宜用that,而不宜用which 的情况如下：
1、先行词为不定代词,all,much,something,everything,anything,nothing,none,the one等。
2、先行词被only, any, few, little, no, just, very, one of等词修饰时。
3、先行词是序数词时或被序数词修饰时。
4、先行词是最高级或被最高级修饰时。
5、先行词既有人又有物,用which和who都不适合,这时宜用that。
6、被修饰词为数词时。
7、如果有两个从句,其中一个关系代词已用which ,另一个关系代词宜用that,以避免语言的单调或重复。
8、疑问词是who或which,关系代词宜用that,以避免重复。
9、主句是There be 结构,修饰其主句的定语从句宜用that 作关系代词。
10、被修饰成分为表语时,或者关系代词本身是定语从句的表语时,该关系代词宜用that。
定语从句中宜用which而不宜用that 的情况：
1、当关系代词的前面有介词时。
2、在非限制性定语从句中。
3、在一个句子中有两个定语从句,其中一个定语从句的关系代词用了that, 另一个宜用which。
4、当关系代词后面带有插入语时。
5、先行词本身是that, 宜用which。
6、先行词是those+复数名词。
主要看修饰的对象。that既可指人也可指物；who只能指人；which只能指物。
He is the man who/ that I saw yesterday.（who/that在从句中作宾语）
A friend who/ that helps you in time of need is a real friend . （who/that在从句中作主语）
一.只能用that作为定语从句的关系代词的情况 ：
1) 在不定代词,如：anything, nothing, everything, all, much, few, any, little等作先行词时,只用that.
All that is needed is a supply of oil.
2) 先行词有the only, the very, the just修饰时,只用that.
He is the very man that helped the girl out of the water .
3) 先行词为序数词(the last)、数词、形容词最高级时,只用that..
The first English book that I read was “The Prince and the Pauper” by Mark Twin .
4) 先行词既有人,又有物时.
He talked about the teachers and schools that he visited .
5)当主句是以who 或which 开始的特殊疑问句时,用that 以避免重复.
Who is the person that is standing at the gate .
二.不能用that的情况，而用which/who：
非限定性定语从句，逗号后面只能用which。
The sun heats the earth, which is very important to us.
关系代词前有介词时.
This is the hotel in which you will stay.如有两个定语从句,其中一句的关系代词是that,另一句宜于用which.
Let me show you the novel that I borrowed from the liberary which was newly open to us.
who,that在很多情况下可以通用,但是有些情况只能用who:
1.先行词是one,ones,anyone的时候宜用who.
Anyone who fails to finish the task given should be criticized.
2.先行词为those的时候,宜用who为关系代词
Those who want to go to the Great Wall sign up here.
3.当先行词有比较长的后置定语的时候
I met a foreigner in the street yesterday who could asked me questions in
Chinese.
4.一个句子中带有两个定语从句,其中一个定语从句的关系代词为that,另一个则用
who.
The boy that you met last night is the group leader who studies very hard.
5.在there be 开头的句子中
There is an old man who wants to see you.that常用作关系代词，可指代某人，也可指代某物，指物时有的时候可用which替换that，指人时可用who替换。但在下列情况下，一般用that。
一、that指代某物事时
1.先行词为all, few, little, much, the one, something, anything, everything, nothing等时。如：
We'll do all that we can to protect the endangered plants and animals.
2. 先行词被all, every, no, some, any, (a)few, (a)little, much等限定词修饰时。如：
You can borrow any book that you want to read in our school library
3. 先行词被序数词或形容词最高级修饰时。如：
This is the most beautiful city that I've ever seen.
4. 先行词被the only, the very, the right, the last 等修饰时。如：
This is the very factory that they visited last summer holiday.
5. 先行词是并列结构，既有人又有物时。如：
He talked happily of the writer and his books that interested him.
6. 先行词前有the same 修饰，表示和先行词是同一物时。如：
This is the same purse that I lost yesterday
7. 先行词为数词时。
Look at the books on the bookshelf. You can see the two that you bought me for my birthday.
8. 如果which引导的定语从句中又含有一个定语从句，为避免重复，第二个定语从句用that。如：
They built a factory which produced things that had never been seen.
9. 以which作主语开头的特殊问句，为了避免重复，定语从句用that。如。
Which is the bus that you will take?
10. 关系代词在定语从句中作表语时，而且通常省略。如：
My hometown is no longer the place that it used to be.
11. 关系代词在there be 句型中作主语时,而且常可以省略。如：
This is the fastest train (that) there has ever been.
二、that 指代某人时。
1. 泛指某人时。如：
He is a man that is never at a loss.
2. 主句是以作主语的who开头的特殊问句，为了避免重复时。如：
Who is the person that is talking with our headmaster?
3. 先行词前有the same时。如：
This is the same man that gave us a talk last year.
4. 关系代词在定语从句中作表语时。如：
He was not the man (that) he was 10 years ago.
另外，that也可用作关系副词，表示时间、地点、原因和方式，在口语中可以用来代替when, where, why 引导的定语从句。在以下名词day, year, time, moment, reason, place等作先行词时，可用that作关系副词引导定语从句。如：
I'll never forget the day (that) I joined the League.
This is the first time that I have been abroad for traveling.
（注：先行词是time,前面有序数词或last修饰时，常用that引导定语从句或者省略。）
当先行词为表示方式的词the way时，可用that引导定语从句, that常可以省略。
I don't the way you speak to her.
怎么说呢，你这样问很难回答你。 定语从句中who是用来修饰人的，that一般情况下可以用来修饰物，有时候用来修饰人。who which that 在定语从句中是充当主语的，他们被称为关系代词。 从网上摘抄了一小段(先行词指的是句子所要修饰的定语，比如说句子 the man who is tom's father dead yeaterday这个句子中the man 就是先行词)
先行词为everything，all，little，much等不定代词时；
先行词被all，every，no，any，some，little，much，one修饰时；
先行词被the only，the very，the same，the last修饰时；
先行词被序数词或形容词最高级修饰时；
先行词是be的表语或there be 的主语时；
先行词有人又有物时；
当主句是以who或which开头的特殊疑问句时。
不能用that的情况
介词前置时；
非限定性定语从句中
先行词本身是that
语法说难不难说易不易，多做做题目，积累下，就好了
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产夏盐酸： 在定语从句中,关系代词who (whom) 和that都可指人和物,在一般情况下,可以互换使用,但在下列情况下值得注意: 一、用who (whom) 而不用that的情形 (1) 在非限制性定语从句中的先行词指人时,只能用who (whom). (2) 当定语从句对指人的...
裕华区19360765735： 定语从句什么时候用that做关系词 - ？
产夏盐酸： 先行词不管是物还是人,都可以用that 做关系词,但是有特殊情况,如下: 习惯上要用that引导的定语从句: (1)当先行词是指物的all, little, few, much, any, anything, everything, nothing, none, the one时,或先行词被all, little, few, much, any, ...
裕华区19360765735： 定语从句中什么时候只能用That - ？
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裕华区19360765735： 定语从句什么时候只能用that - ？
产夏盐酸： (1)先行词是不定代词或者先行词被不定代词所修饰时, 关系代词通常只用that, 不用which.例如:① That's all that I know. 我知道的就这些.② Is there anything that you want to buy in town? 你有什么东西要在城里买吗? ③ Nothing that the ...
裕华区19360765735： 什么时候的定语从句只能用that - ？
产夏盐酸： 定语从句只能用that (1) 如果先行词是all, much, anything, something, nothing, everything, little, none等不定代词,关系代词一般只用that,不用which.例如: All the people that are present burst into tears.Is there anything that I can do ...
裕华区19360765735： 在定语从语中,什么时候用THAT,什么时候用WHICH? - ？
产夏盐酸： 只能用that的情况: <1>关系代词在定语从句中作表语,不管是人或物只能用that. He is not the man that he was when I first saw him. 【他现在不是我第一次见他时那样的.】<2>当先行词即指物又指人时,多用that引导定语从句. Look at the ...
裕华区19360765735： 定语从句中 什么时候必须用that - ？
产夏盐酸：[答案] 省略宾语的情况是:后面所跟的从句缺宾语,其他情况that 都不省略
裕华区19360765735： 定语从句that的用法!什么时候能用that什么时候不能用that什么时候只能用which什么时候只能用of+介词不能用指示副词 - ？
产夏盐酸：[答案] 一般来说关系代词which和that可以互换,但这几种情况下不能用that,只能用which:在非限制性定语从句里、关系代词前面出现介词提前.这几种情况下只能用that不能用which:先行词前面出现最高级,序数词和there be修饰、先行词既有人又有物. ...
裕华区19360765735： 定语从句中,什么时候用that ,什么时候用which? - ？
产夏盐酸：[答案] 定语从句(Attributive Clauses)在句中做定语,修饰一个名词或代词,有时也可以修饰部分或整个句子. 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, ...
裕华区19360765735： 定语从句中的连接词什么时候一定要用that? - ？
产夏盐酸： 指人, 物,做主语,宾语, 表语时可以用 在指物的先行词被序数词,最高级, any all 等词修饰,或是先行词是anything, nothing much, all 等不定代词时一定要用 如不明白请追问,如果满意请【采纳】 祝学习进步
