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。下面是小编为你带来的英语定语从句说课稿 ，欢迎阅读。
一， 定义：在复合句中作定语，修饰主句中某一名词或代词的从句，叫做定语从句。被定语从句所修饰的词叫先行词，通常位于定语从句前。引导定语从句的是关系代词（that,which,who,whom,whose）和关系副词（when,where,why），它们既起连接作用，又充当从句中的一个成分，如何使用关系代词或副词是根据先行词及其在从句中所充当的成分确定的。
二，关系代词引导的定语从句
人 | 物 | 人+物 | |
主 语 | who/that | which/that | that |
宾 语 | who(m)/that | which/that | that |
定 语 | whose/of whom | whose/of which | whose |
表 语 | who/that | which/that | that |
注：如果关系代词在从句中作主语，从句谓语动词的人称和数必须和先行词一致。
①China is a big country that/which has a history of about 5000 years.
②Phil who/that comes from England is an active boy.
③The doctor (who/whom) David saw at the hospital told me to stop smoking.
④We passed some shops whose windows were decorated for Christmas.
⑤Is this the book (that/which) he is looking for?
△重点
1.that,who和which在从句中作主语时不可省略，作宾语时可省略。（但whom/which前有介词时，whom/which不能省略）
e.g. The man (who/whom) my father is talking with is my teacher.
The man with whom my father is talking is my teacher.
2．关系代词在从句中作介词宾语时可跟介词一起放在先行词后面；为了使关系代词紧跟它所修饰的先行词，也可把介词放在从句中有关动词的后面。但固定短语中的介词不要放在先行词前（如look for,look after,take care of等）
e.g. The boy who(m) she is looking after is her aunt’s child.
3.that与which先行词都可指物，that与who/whom先行词都可指人，很多情况可互换使用，但也有区别。
A.只用that不用which的情况
1）当先行词是指物的不定代词all,much,little,something,everything,anything,nothing,none,the one时。
e.g. I’m interested in everything that I don’t know.
2)当先行词被(the)only,the very,the last,all,some,any,no,every,little,few,much等修饰时。
e.g. There is no difficulty that we can’t overcome.
3)先行词前有序数词、形容词最高级修饰时或先行词本身就是序数词或形容词最高级时。
e.g. The first lesson that we’re going to learn is very difficult.
4)先行词为两个及两个以上分别表示人和物的名词时。
e.g. We know nothing about the doctors and the hospitals that you are talking about.
5)当主语是以who或which开始的疑问句时。
e.g. Who is the boy that was here just now?
6)关系代词在定语从句中作表语时。
e.g. The village is no longer the poor place that it used to be.
7)先行词有the same修饰，先行词和关系代词指同一物时。
e.g. This is the same pen that I used yesterday.
B.只用which不用that的情况
1）关系代词前有介词时。
e.g. This is the room in which we lived last year.
2)引导非限制性定语从句时。
e.g. His dog,which was very old,became ill and died.
3)先行词后有插入语时。
e.g. Here is the grammar book which,as I’ve told you,will help improve our English.
4)先行词本身是that时。
e.g. What’s that which flashed in the sky just now?
C.先行词指人，但只用who不用that的情况。
1）先行词是指人的不定代词时，如one,someone,anyone,no one,all,nobody,none,those等。
e.g. Those who are against put up your hands.
2)当先行词是一个限定性的表示人的特定名词时。
e.g. The aunt who came to see me last week is my father’s sister.
3)当先行词有较长的后置定语或在被分割的定语从句中。
e.g. Mr.White is coming soon who will give us a talk.
4)whose+n.=the+n.+of which/whom
e.g. We live in the room,whose window is broken.(=the window of which is broken.)
注意：which与whose作定语时的区别
which只用于非限制性定语从句，仅指物，且要修饰对先行词起概括作用的泛指名词；“whose+n.”与先行词不表示同一事物或情况。
e.g. ①Mary is studying Chinese,which knowledge is important now.
②The man whose wife is a housewife is from France.
△难点：关系代词as引导的定语从句
as既可引导限制性定语从句，也可引导非限制性定语从句，as在从句中作主语、宾语或表语。
引导限制性定语从句，常用于以下句式。
1） such+n.+as…：“像….一样的”
the same+n.+as…：“和…同样的”（指同类异物，同类同物用that）
e.g. ①These houses are sold at such a low price as people expected.
② I want to buy the same cellphone as you bought.
The same customer that came here yesterday is here again.
2)…such as…
such意为“这样的人或物”，修饰先行词such.
e.g. This book is not such as I expect.
关系代词as与which引导非限制性定语从句的区别：as引导的非限制性定语从句，既可在主句前，又可在主句后，有时还可插入主句中，而which引导的'非限制性定语从句只能置于主句之后。相同的是两者都可替代主句的整个内容，而不是主句中的某一个词。
e.g. ①As is known to everybody,the moon travels round the earth once every month.
3．当定语从句放在主句后面时，也并非as永远等于which。
1）当非限制性定语从句是否定句或表示否定时只用which。
e.g. He came here very late,which was unexpected(not expected).
2） 当as在从句中作主语时，后面常跟动词的被动式。如be known,be said,be reported,be announced等。若从句中动词是主动式，一般用which作主语。
e.g. ①She’s been absent again,as is expected.
②Tom has made great progress,which makes us very happy.
3)当非限制性定语从句的谓语是一个复合结构时，只能用which引导定语从句。
e.g. Betty always tells a lie,which her parents find strange.
4)as多用于下列习惯用语中：
as anybody can see as is well-known=as is known to all
as we had expected as often happens
as has been said before as is mentioned above
as (it) seems likely as (it) pointed out
as I remember (it) as I understand (it)
as (it) appears
e.g. Jack has won the first prize,as it often happens.