定语从句也称关系从句、形容词性从句，一个句子跟在一名词或代词（先行词）后进行修饰限定，就叫做定语从句。通俗来讲，从句在整个句子中做定语，这个从句就叫做定语从句。
从句在主句中充当定语成分，被修饰的词叫先行词。定语从句不同于单词作定语的情况，它通常只能放在被修饰的词（即先行词）之后。定语从句由关系词（关系代词、关系副词）引导，关系代词、关系副词位于定语从句句首。
1、关系代词引导的定语从句
①who, 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?
他就是想见你的人吗？（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）
②Whose 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。
③which, 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在从句中作主语）
The package which / that you are carrying is about to come unwrapped.
你拿的包快散了。(which / that 在从句中作宾语）
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。
①when, 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.
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？
②that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，在非正式文体中that常被省略（正式文体中不可省略），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。
定语从句是什么
定语从句，就是用来修饰名词或代词的句子，起到定语的作用，所以叫做 定语从句。 定义 被修饰的词叫先行词。定语从句不同于单词作定语的情况，它需要放在被修饰的词（即先行词）之后。定语从句一般由 关系代词来引导。关系代词必须放在定语从句之首。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? 他就是想见你的人吗？（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在句中作主语） 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） 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。 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。
什么是定语从句？
定语从句，一个简单句跟在一名词或代词后（先行词）进行修饰限定，就叫做定语从句。在主句中充当定语成分。被修饰的词叫先行词。定语从句不同于单词作定语的情况，它通常只能放在被修饰的词（即先行词）之后。
定语 从句由关系词（关系代词、关系副词）引导，关系代词、关系副词位于定语从句句首。
扩展资料：
从句结构
定语从句公式：定语从句=先行词+关系词+从句
先行词：指被定语从句修饰的名词、代词或句子。一般先行词出现在定语从句的前面。
关系词：关系词常有3个作用：
①连接作用，连接主句和定语从句。
②指代先行词。
③在定语从句中担当成分。
参考资料来源：百度百科-定语从句
定语从句是什么?
定语从句的分类：
限制性定语从句和非限制性的定语从句
限制性定语从句不用逗号与主句分开，对所修饰的词起特指或限定的作用，去掉后意思不完整或不太清楚。翻译成中文时，一般把定语从句翻译在先行词之前。
引导限制性定语从句的关系代词有who,
whom,
whose,
that,
which,
of
which和关系副词when,
where,
why等。
eg.
This
is
the
man
who
helped
me.
I
was
the
only
person
in
our
office
that
was
invite
to
the
palace
ball.
非限制性的定语从句和主句之间往往用逗号分开，只对被修饰的词语或主句起补充说明的作用，去掉后对句意影响不大。翻译时通常把定语从句翻译在先行词后边，作为附加说明。
引导非限制性定语从句的关系代词有who,whom,
whose,
which,
as和关系副词when,
where，一般不用that
引导。
eg.
I
have
two
sisters,
who
are
both
doctors.
Last
Sunday
they
reached
Shanghai,
where
a
meeting
was
holding.
定语从句的考查热点
1.间隔式定语从句
定语从句一般紧跟在先行词之后，但定语从句先
行词之间有时会插入别的成分，构成先行词与定
语从句的隔离。
eg.
This
is
the
article
written
by
him
that
I
spoke
to
you
about.
He
was
the
only
person
in
this
country
that
was
invited.
(1).
因定语从句过长，为使句子保持平衡，通常定语从句和其所修饰的名词或代词分开。
eg.
The
film
brought
the
hours
back
to
me
when
I
was
taken
good
care
of
in
that
faraway
villiage.
(2).
在定语从句中使用“插入语”以增加句子的灵活性。
eg.
Kate
was
always
speaking
highly
of
her
role
in
the
play,
which,
of
course,
made
the
others
unhappy.
The
pen
I
thought
I
had
lost
is
on
my
desk,
right
under
my
nose.
2.定语从句中的谓语动词与先行词保持一致。
当引导定语从句的关系代词在从句中做主语时，定
语从句的谓语动词的数的形式应与先行词保持一致。
eg.
I,
who
am
your
classmate,
will
try
my
best
to
help
you.
He,
who
is
your
classmate,
will
try
his
best
to
help
you.
注意句式：
one
of
+
复数名词+关系代词+复数动词
the
(only/very)
one
of
+复数名词+关系代词+单数动词
He
is
one
of
the
students
who
have
made
great
progress.
Tom
is
the
only
one
of
my
friends
who
has
been
abroad.
