A. 英语语法，定语从句
不是省略先行词 而是省略关系代词，关系代词在从句中作间接宾语，一般应该用介词to/for加关系代词表达 即相当于间接宾语。如果关系代词前面有介词，则关系代词不能省略，如果介词在定从末尾，则关系代词可以省略。
如he is the man to whom I gave the book.
He is the man (who/whom）i gave the book to。
B. 英语语法中的定语从句的用法请讲解下。
定语从句
（一）定语从句一般由关系代词和关系副词引导
1、关系代词：who, whom, whose, which, that, as
2、关系副词：when, where, why
关系代词和关系副词必须位于从句之首，主句先行词之后，起着连接先行词和从句的作用，同时在从句中又充当句子成分。
e.g. She is the girl who sings best of all.（关系代词who在从句中作主语）
The comrade with whom I came knows French.（whom在从句中作介词with的宾语）
3、关系代词和关系副词的用法：1）当先行词为人时用who 作主语，whom作宾语；2）当先行词为物或整个句子时用which ，可作主语或宾语；3）先行词为人、物时用that ，可作主语或宾语；4）whose用作定语，可指人或物；5）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）。
（二）限制性定语从句与非限制性定语从句
1、限制性定语从句：从句与主句关系密切，去掉从句，主句意义不完整，甚至不合逻辑。
e.g. I was the only person in our office who was invited.（去掉定语从句，意思就不完整）
2、非限制性定语从句：从句对先行词关系不密切，去掉定从句，意思仍然完整。形式上用逗号隔开，不能that用引导。
e.g. Tom’s father, who is over sixty, still works hard day and night.（who引导非限制性定语从句，整个句子可分成两句来翻译）
（三）使用定语从句时特别注意的几个问题
1、that与which的区别。
1）用that而不用 which的情况：①先行词为不定代词all, anything, nothing, …；②先行词有最高级修饰，有序数词修饰；③先行词有only, very, any等词修饰；④先行词既有人又有物时。
e.g. There is nothing that can prevent him from doing it. 没有什么能阻止他不干那件事。
The first place that they visited in Guilin was Elephant Trunk Hill. 在桂林他们所参观的第一个地方是象鼻山。
This is the best film that I have ever seen. 这部电影是我看过的最好的一部。
Mr Smith is the only foreigner that he knows. 史密斯先生是他认识的唯一的外国人。
2）用which而不用 that的情况：①引导非限制性定语从句；②代表整个主句的意思；③介词 + 关系代词。
e.g. He had failed in the maths exam, which made his father very angry. 他数学考试没有及格，这使他的父亲很生气。
This is the room in which my father lived last year. 这是父亲去年居住过的房子。
3）as引导定语从句时的用法
①as引导限制性定语从句通常用于the same … as, such … as结构中。
e.g. I want the same shirt as my friend’s. 我要一件跟我朋友一样的衬衫。
Such machines as are used in our workshop are made in China. 我们车间使用的这种机器是中国制造的。
②as引导非限制性定语从句既可放在主句之前，也可放在主句之后，用来修饰整个句子。通常用下列句型：as is known to all, as is said, as is reported, as is announced, as we all know, as I expect 等。
e.g. As I expected, he got the first place again in this mid-term examination. 正如我所预料的那样，他在这次期中考试中又获得了第一名。
3）as 引导非限制性定语从句时与which的区别
①当主句和从句语义一致时，用as；反之，用which来引导非限制性定语从句。
e.g. He made a long speech, as we expected.
He made a long speech, which was unexpected.
②当非限制定语从句为否定时，常用which引导。
e.g. Tom drinks a lot every day, which his wife doesn’t like at all.
2. 关系代词在从句中作主语时，从句的谓语动词单数还是用复数应由先行词决定。
e.g. The man who lives downstairs speaks English fluently. 住在楼下的那个人英语说得很流利。
The students who are in Grade Three are going to climb the hill tomorrow.
3. 定语从句有时不直接紧靠先行词，中间由一个定语、状语或谓语隔开。
e.g. There is an expression in his eyes that I can’t understand.
4. 引导定语从句的关系副词有时可以用“介词 + which”来代替。
e.g. October 1, 1949 was the day on which ( = when ) the People’s Republic of China was founded.
5. 当定语从句中谓语动词是带介词或副词的固定短语动词时，短语动词的各个固定部分不要拆开。
e.g. The sick man whom she is looking after is her father.
6. 介词在关系代词前，只能用which和whom，且不能省略；介词在句尾，关系代词可有which, that, whom, 口语中也可用who，且可省略。
e.g. The man (whom/ who/ that) you were talking about has come to school.
C. 英语－语法－定语从句
两种，1.限制性定语从句由that.介词+which.who.whom.the one引导，2.非限制性定语从句由as.which.who.whom等引导“，”是非限制性定语从句的标志回。
非限制性定语从句引导词代替的是前面的句子做从句的成分，限答制性定语从句中没逗号，明白？
只能用“that”的情况：
1.the only+sth.（sth.为先行词)
2.all作先行词（1）指人用who（2）指物用that
3.若先行词和引导词间隔了一个单词或成分用that
只能用“who”的情况：
1.先行词为one、ones、anyone
2.先行词为those
3.先行词有较长的后置定语
4.句子中有两个定语从句后一个的引导词用who
5.there be开头的句子
这都是长时间的积累，希望对你有用
D. 英语语法定语从句
1.定语从句的定义：用作定语的从句叫定语从句。
2.先行词：被定语从句所修饰的名词或代词。
3.定语从句的位置：紧跟先行词(名词或代词)之后。
4.引导词：引导定语从句的词(包括关系代词和关系副词)。
﹙1﹚关系代词：that/who/whom/which/as
﹙2﹚关系副词：when/where/why
5.引导词的位置：位于定语从句之前(先行词之后)。【as除外】
6.引导词的功能(作用)：
﹙1﹚连接先行词和定语从句。
﹙2﹚在定语从句中充当一定的成分(关系代词充当主语或宾语，关系副词充当状语)。
7.定语从句的类型：
﹙1﹚限定性定语从句(主句和定语从句之间无逗号)。
①
直接由引导词引导定语从句
The
man
who
you’re
talking
to
is
my
friend.
②
由介词+关系代词(whom/which)引导
The
man
to
whom
you’re
talking
is
my
friend.
I
need
a
pen
with
which
I
can
write
a
letter.
=I
need
a
piece
of
paper
on
which
I
can
write
a
letter.
介词的选用可根据从句中的相关词组确定，该介词通常可以放在关系代词之前，也可放在从句之尾。例如：
The
man
(who/whom/that)
I
talked
about
at
the
meeting
is
from
Beijing
University.
=The
man
about
whom
I
talked
at
the
meeting
is
from
Beijing
University.
The
palace
(which/that)
I
often
pay
a
visit
to
was
built
in
the
17th
century.
=The
palace
to
which
I
often
pay
a
visit
was
built
in
the
17th
century.
﹙2﹚非限定性定语从句(主句和定语从句之间用逗号隔开)。
①
直接由引导词引导定语从句。
②
由介词+关系代词(whom/which)引导。
I
live
in
a
house
far
away
from
the
city，
in
front
of
which
is
a
big
tree.
There
is
an
apple
tree
standing
at
the
gate，
on
which
are
many
apples.
This
is
the
man
to
whom
I
gave
the
book.
③
由“代词/名词+of+whom/which”或“of
which/
whom
+名词/代词”(先行词指
人用whom，指物用which)引导。One，
some，
any，
none，
all，
both，
several，
many，
most，
neither，
either等词、数词、分数或百分比与of
whom或of
which连用。
He
has
five
children，
two
of
whom
are
abroad.
(比较：He
has
five
children，
and
two
of
them
are
abroad.)
We
have
three
books，
none
of
which
is/are
interesting.
(比较：We
have
three
books，
but
none
of
them
is/are
interesting.)
除why和that不能引导非限定性定语从句外，其余引导词都可以，用法同限定性定语从句一样。但要注意以下区别。
1.在形式上非限定性定语从句与主句有逗号隔开。
2.非限定性定语从句的作用：它只是补充说明先行词的情况，翻译时可译成两个句子。
The
engineer，
whose
leg
was
badly
hurt，
was
quickly
sent
to
hospital.
(那位工程师被很快送往医院，其腿部受了重伤)
The
engineer
whose
leg
was
badly
hurt
was
quickly
sent
to
hospital.
(那位腿部受了重伤的工程师被很快送往医院)
3.在非限定性定语从句中，任何引导词都不能省略(包括引导词在此定语从句中充当宾语在内)。指人做主语时只能用who，
做宾语时用whom；
指物做主语，宾语都用which；
关系副词用when或where，也不能省略。
E. 英语语法 定语从句
这明显是语法错误，书中例句是有问题的，因为从句完整，所以应该用关系副词when
F. 英语定语从句的主要语法
关系词的选用是重点
一. 选准关系代词和关系副词
在定语从句中，关系代词或关系副词都代替先行词在从句中充当一定的成分，如果该从句中缺少主语、表语、宾语或定语，就要用关系代词来连接从句；如果从句中缺少状语，就得用关系副词来连接从句。例如：
（1）I still remember the days which / that we spent together .
（2）I still remember the days when we worked together .
二. 了解仅用that 引导限制性定语从句的几种情况
that 在限制性定语从句中既可指人又可指事或物。在下列情况下，只能用that 来引导定语从句：
1. 先行词是all , much , few , little , everything , anything , nothing 等不定代词时。例如：
Is there anything that you want to buy ?
2. 先行词被all , few , little , much , every , some , no 等词修饰或被the only , the very , the same , the last 等限定词修饰时。例如：
These are all the pictures that I have seen .
This is the very dictionary that is of great help .
3. 先行词既指人又指物时。例如：
My father and his teacher talked a lot about the things and the persons that they could remember .
4. 关系代词在定语从句中作表语时。例如：
Our school is not the one that it used to be .
5. 先行词被形容词最高级或序数词修饰时。例如：
This is the best English film that I have ever seen .
The first English novel that I read was A Tale of Two Cities .
6. 主句是who 或which 引导的特殊问句时。例如：
Who is the girl that is standing under the tree ?
Which is the machine that we used last Sunday ?
三. 把握“介词＋关系代词”结构中介词的选用
介词的选择与主句中先行词的搭配密切相关。例如：
That”s the reason for which he was late for school .
This is the book on which I spent 8 yuan .
注意：
1. 定语从句中谓语动词是含有介词的动词短语时，介词应放在动词之后，不能拆开放在关系代词前。例如：
This is the key which you are looking for .
This is the baby whom you will look after.
2. 该结构中，关系代词指人时用whom，指物时用which .
四. 弄清as 和which 引导的非限制性定语从句指代整体时的区别
1. 位置上的区别：as 引导的非限制性定语从句的位置比较灵活，可以放在主句前，也可以放在主句后，还可插在主句的中间；而which 引导的非限制性定语从句只能放在主句之后。例如：
As is known to us all , the earth turns around the sun .
The earth , as is known to us all , turns around the sun .
The earth turns around the sun , as is known to us all .
The earth turns around the sun , which our parents once told us when we were very young .
2. 词义与联系上的区别：as 引导的非限制性定语从句与主句之间有着较为密切的上下文联系，as 本身含有“正如”之意；而which 引导的非限制性定语从句与主句之间在逻辑意义上近似并列句，which 本身表示“这”或“这一点”之意。例如：
Light travels faster than sound , as we all know .
Jack came late for school , which made his teacher angry .
五. 注意定语从句的主谓一致性
关系代词在定语从句中作主语时，从句的谓语必须与先行词保持人称和数的一致。例如：
Tom is one of the boys who are from the USA.
Tom is the only one of the the boys who is from the USA.
六. 保持主句的完整性并避免从句成分的重叠
1. 在定语从句中，不管出现任何情况，主句的结构必须完整，即主句必须有主语和谓语，缺一不可，否则，整个主从复合句就无法成立。试比较：
（1）Is this factory _____________ we visited last week ?
（2）Is this the factory ____________ we visited last week ?
A. which B. where C. what D. the one
分析：
第一题缺少表语，只有填D项才能保持主句的完整性，而其他的选项均为干扰项。
第二题主句本身完整，应填的关系代词在从句中作visited 的宾语，故应选A项。
2. 从定语从句中，关系代词或关系副词已经代替先行词独立地或与相应的介词一起在定语从句中充当了一定的成分，因此在定语从句中就不能再出现与关系代（副）词重叠的成分。例如：
错句：Is this the train that they took it last Sunday ?
分析：该题中that 已经代替先行词the train 在定语从句中充当及物动词took 的宾语，故重叠出现的宾语it必须删去
G. 英语语法 定语从句
这些你还是自己看抄书吧，平时认真听课。这里和你讲也会很复杂的
定语从句大类分成限制性和非限制性。
其中限制性定语从句中又有对事物的修饰，对人的修饰以及对人和物共同的修饰。
如果事物作为修行词且没有序数词，最高级的情况下，用that
或
which
，如果做状语，则要用when，where或in
which
如果先行词是一个原因，用why或者for
which
如果先行词是一个人，用who
如果先行词是不定代词，序数词，最高级，关联词只能用that
如果先行词在定语从句中做宾语成分，关联词可以不需要。
H. 英语定语从句，语法
定语从句中，连接先行词和定语的叫关系代词或关系副词。有一些情况下，关系代词可以省略：
1、当关系代词所代替的先行词在定语从句中做宾语，关系词可以省略。Whoistheman(that/who/whom)youweretalkingto? 刚才和你讲话的人是谁？
2、当关系代词that在定语从句中用作表语时，可以省略。
Chinaisnotthecountry(that)itwas. 中国已不是过去的中国了。
3、关系副词when用于day,year,time少数词后时可以省略（也可换成that）Thatwastheyear(that)Ifirstwentabroad. 就是那一年我第一次出国。
4、关系副词where用于place, somewhere, anywhere, everywhere, nowhere少数词后时可以省略(也可换成that)。
Thisistheplace(where)theymetyesterday. 这就是他们昨天碰头的地方。
5、当关系代词that在定语从句中用作宾语补足时，可以省略。
I’mnotthemadman(that)youthoughtme. 我并不是你所认为的那个疯子。
6、关系副词why通常只用于the reason后引导定语从句，且通常可换成that或for which，这些连接词都可以省略。
That’s the reason (why, for which, that) he came. 这就是他来的原因。
Give me one reason (why) we should help you. 给我举出一个我们应当帮助你的理由。
如有疑问，请追问，满意，请采纳，谢谢。