雅思考试中并没有很直接的考察语法，但是却在字里行间隐藏着对语法的考察。学会语法，就会发现自己组织语言、写作逻辑、阅读能力都在不知不觉中提升很多。希望这篇英语语法之定语从句的用法分享可以让大家对定语从句更加了解。
一、定语从句简介
所谓从句，就是一个主谓结构相当于整个句子(这样的句子叫复合句)的一个成分，因此，从句不能单独使用。在复合句中修饰名词或代词、作定语的句子叫定语从句。定语从句是中国人学英语的难点之一。
其实定语从句很有规律，总结如下：在关系代词中that既可指人又可指物、既可作主语又可作宾语，因此，除了在非限定性定语从句中，用that一般不会出问题。关系副词的用法比较单一，它们从句中只起状语的作用，表示时间的就用when，表示地点的就用where，而why只修饰一个词，即reason。
定语从句所修饰的词叫“先行词”，因为它总是处在定语从句的前头，比定语从句先行一步。
引导定语从句的词叫关系词，包括关系代词和关系副词。
关系代词：
who, which, that作从句的主语
whom, which, that 作从句的宾语(可省略)
whose从句中作定语
以下情况只能用that, 不能用which:
①先行词为不定代词all, little, none, any, every, no ,much, anything, nothing
②先行词有最高级和序数词修饰时(包括the only, the very, the same, the last, the next等)
③先行词既有人又有物的时候
以下情况只能用which, 不能用that:
①引导非限制性定语从句(包括代表整个主句的意思时)
②介词+关系代词的结构中
关系副词：
when 指时间，在定语从句中作时间状语
where 指地点，在定语从句中作地点状语
why 指原因，在定语从句中作原因状语，只修饰reason。
如果用定语从句把两个句子合二为一：首先找出两个句子当中相同的部分，定语从句修饰的就是这一部分。要把其中一个句子变成定语从句，就要把这句中相同的那个部分用一个关系词来代替;代替时，先看被代替的部分是指人还是指物、再看它作什么句成分。
指人并作主语的，就用who或that;指人并作宾语的，就用whom或that;指人并作定语的，就用whose。指物并作主语的，就用which或that;指物并作宾语的，还是用which或that;是物并作定语的，就用whose或of which。这样找好并替换以后，再把这个关系代词放到要变成定语从句的那个句子的最前面(被代替的部分不能再保留，其它的词语一律不变)，这个句子就变成了定语从句。
然后，再把这个定语从句整个放在被修饰的词后面，最后，如果还有其它句子成分，就把它们放到定语从句的后面，就行了。
例如：Have you found the book?
You were looking for the book yesterday.
在这两个句子中，the book是相同的，定语从句修饰的就是the book。把后面这一句变成定语从句，找个关系词来代替the book;在将要被变成定语从句的名子中，the book是物并作宾语，所以用which 或that代替它。然后把which 或that放到本句的最前面，其它的词和语序一律不变。
这时，就成了“that/which you were looking for yesterday?”，再把这个定语从句整个放在被修饰的词后面，就成了 “Have you found the book that/which you were looking for yesterday?” 定语从句就完成了，主句是问句，所以句末用问号。
that/which代替的是原句中的宾语，原句变成了从句，它们仍然作从句的宾语。关系代词在从句中作宾语时可以省略，因此上句又可变成“Have you found the book you were looking for yesterday?”
请同学们照上面的例子，把下面变定语从句的步骤说出来(括号里的可以省略)：
(1)“The dog belongs to the Browns. It ate my fish yesterday.”
→The dog which/that ate my fish yesterday belongs to the Browns。
(2)“The lady has gone to the police station. Her car has been stolen.”
→The lady whose car has been stolen has gone to the police station.
(3)“I’ve seen the film. His girl friend played the leading role in it.”
→I’ve seen the film (which / that) his girl friend played the leading role in.
→I’ve seen the film in which his girl friend played the leading role.
→His girl friend played the leading role in the film (which/that) I’ve seen.
关系副词与此同理。只是关系副词代替的是原句中的状语。在被代替之前，这个状语中一定要含有一个与另一句相同的成分。
例如：This is the house.
I was born and brought up in the house.
在这两个句子中，in the house 是句子里的地点状语，定语从句修饰的就是the house 。 把后面这一句变成定语从句。在将要被变成定语从句的句子中，in the house 是地点状语，所以用where来代替它。然后再把where放到本句的最前面，其它的词和语序来代替它。
然后再把where放到本句的最前面，其它的词和语序一律不变。这时，就成了“where I was born and brought up”。再把这个定语从句整个放在被修饰的词后面，就成了“This is the house where I was born and brought up.”，定语从句就完成了，主句是陈述句，所以句末用句号。Where代替的是原句中的状语，原句变成了从句，它就作从句的状语。
请读者照上面的例子，把下面变定语从句的步骤说出来(括号里的可以省略)：
(4)The hotel is an artistic building. We’ll stay in it.
→The hotel where we’ll stay is an artistic building.
→The hotel (which/that) we’ll stay in is an artistic building.
→The hotel in which we’ll stay is an artistic building.
(5)Perhaps they’ve heard of the place. We went there for our holidays last time.
→Perhaps they’re heard of the place where we went for our holidays last time.
(6)They’re redecorating the room. A conference will be held in the room.
→They’re redecorating the room where a conference will be held.
→They’re redecorating the room (which /that) a conference will be held in.
→They’re redecorating the room in which a conference will be held.
那么，“介词+关系代词”是怎么回事呢?原来上面这个例句，还有一种做法：This is the house.
I was born and brought up in the house.
在这两个句子中，the house是相同的，定语从句修饰的就是the house 。把后面这一句变成定语从句。在将要被变成定语从句的句子中，the house表示物而且是介词in的宾语，所以用关系代词which或that来代替。然后把which或that放到本句的最前面，其它的词和语序一律不变。
这时，后面这一句就成了 “which/that I was born and brought up in”。再把这个定语从句整个放在被修饰的词后面，就成了“This is the house which/that I was born and brought up in”。定语从句就完成了，主句是陈述句，所以句末用句号。
which/that代替的是原句中的宾语，原句变成了从句，它们就作从句的宾语。关系代词在从句中作宾语时可以省略，因此上句又可变成“This is the house I was born and brought up in.”
但是，in可以提到关系代词的前面，不过这时不能用that，而且不能省略。所以上句又可变为“This is the house in which I was born and brought up.”这就是“介词+关系代词”的来历。
上面就是对英语定语从句中先行词和关系词的讲解，希望大家能够掌握并灵活运用，更多备考经验请大家持续关注前程百利雅思频道。最后，小编祝大家拿到满意的雅思成绩。
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