这个句型是这单元我们重点接触的一个语法项目，你观察两个句子，看看有什么区别:
一本有趣的书
an interesting book 形容词interesting做定语修饰名词book
a book that is interesting that is interesting这个句子做定语修饰名词book
interesting/that is interesting作用是相同的,都是用作定语来修饰名词book, 我们把这种在复合句中修饰名词或代词的从句叫做定语从句。再如:
一位漂亮的女孩
a girl who is beautiful 从句做定语（girl是先行词）
等于a beautiful girl beautiful是形容词做定语
一本有趣的书
a book that is interesting 从句做定语（book是先行词）
等于an interesting book 形容词做定语
复合句中，修饰某一名词或代词的从句叫做定语从句。既这个从句起的作用与形容词完全一样，起修饰和限定主句里名词的作用。可以形容人，物和事件，在主句中充当定语的作用。试比较：
I like quiet music.
I like music that is quiet.
定语从句要跟在所修饰的名词或代词后面，被定语从句修饰的名词或代词叫做先行词。定语从句一般用关系代词who，that，which和whose来引导，放在从句的句首使从句与主句相连，并在句中担当一定的成分，关系代词如果在从句中作主语就要用主格，如果做宾语就要用宾格，如果做定语就要用所有格。
I like music that I can dance to. 我喜欢可以随之跳舞的音乐。
music作先行词，that I can dance to 是定语从句修饰music，其中，that是关系代词引导定语从句
I prefer singers who can write their own songs. 我喜爱能自己写歌的歌星。
singers作先行词，who can write their own songs 是定语从句修饰singers，其中，who是关系代词。
定语从句是高中的一个重要语法项目，这里就各关系代词举例如下：
That在从句中作主语或宾语(作宾语时that 可省略)指物
1.A plane is a machine that can fly. (作主语)
2.The noodles （that） I cooked were delicious. (作宾语)
指人
1.Who is the man that is reading the book over there? (作主语)
2.The girl (that) we say yesterday was Jim’s sister. (作宾语)
Who / that 在定语从句中做主语时，需要注意的是谓语动词的单复数应与先行词保持一致。例如:
I like a sandwich that is really delicious.
I love singers who are beautiful.
I have a friend who plays sports.
I prefer shoes that are cool.
Which在从句中作主语或宾语(作宾语时可省略) 指物
1.The silk which is produced in Hangzhou sells well. (作主语)
2.The songs （which） Liu Dehua sang were very popular. (作宾语)
Who, whom在从句中分别作主语和宾语（若介词放在从句后面，则whom可以省略）指人
1.The foreigner who visited our class yesterday is from Canada. (作主语)
2.The boy who break the window is called Roy. (作主语)
3.The person to whom you just talked is Mr Li. (作宾语)
4.Mrs White is the person to whom you should write. (作宾语)
Whose 在从句中作定语指人或物的所有格
I like the girl whose hair is long. (作定语)
任务设计
任务I. 阅读下列句子，再用who/that 填空。
1.I have a brother ____ likes soccer.
2.Tom doesn’t like movies _____ are too long and too scary.
3. We prefer groups _______ play loud and energetic songs.
4. He likes friends _______ often help each other.
任务II. 请将下列题中的两个句子合并成一个句子。
1. I like music.
The music is loud and exciting.
______________________________________.
2. She loves movies.
The movies are romantic.
_____________________________________.
3. Tony likes music.
He can dance to the music.
______________________________________.
任务III. 请完成下列句子。
1. I like singers who_______.
I prefer singers who______.
He likes singers who_______.
She prefers singers who____.
2. I like mobile phones that____.
3. I like ( )that_____
Key:
任务I.
who, that, that, who
任务II.
1. I like music that is loud and exciting.
2. She loves movies that are romantic.
3.Tony likes music that he can dance to.
任务III.
1. can write their own songs (这四句答案可相同。)
2. look cool
3. books, tell about how to become a good tennis player.
1.that的必用。。1先行词是最高级 2是序数词 3不定代词 4先行词即指人又指物 5被only；the，every, any, all, some, no, little, few, much等修饰时等修饰 6主句有which；who；whom 7there be 句型中 （指物）
2. that在作宾语时可省
【考点归纳】定语从句中常见的关系代词有who（whom），whose，that和which，它们的用法分别为：
① who用来代人（即它的先行词必须是人），在从句中可担任主语和宾语。但who的前面不能有介词，如果带介词，则必须用宾格的whom ：介词＋whom。如：
He is the boy with whom I went there．他就是和我一起去那儿的男孩。
另外，当关系代词that用来代人时，关系代词who和that在许多情况下可以通用。但有时须用who，而不用that：
a．先行词是one，ones，anyone和those时，须用who。如：
One who has nothing to fear for oneself dares to tell the truth．
一个无所畏惧的人敢于说实话。
b．在there be开头的句子中。如：
There is an old man who wants to see you．有位老人要见你。
c．一个句子带有两个定语从句，其中一个定语从句的关系代词是that，另一个须用 who。如：
The girl that you met last week is the monitor who studies very hard．
上周你遇到的那位女孩是位学习非常努力的班长。
② whose是代词的所有格，它既可以代人也可以代物。当whose代物时，它相当于… of which。如：
Please show me the book whose cover is black．
＝Please show me the book，the cover of which is black．
请把封面是黑色的书拿给我看看。
③ 当that和which在限定性定语从句中代物时，which常可以和that通用，但有时只宜用which，不用that：
a．关系代词前有介词。如：
This is the room in which you will stay．这将是你住的房间。
b．如果两个定语从句，其中一句的关系词是that，另一句宜用which。如：
Let me show you the book that I borrowed from the library，which was newly open to us．
让我给你看看我从重新开放的图书馆借来的书。
另外，非限定性定语从句中，只宜用 which，不能用that。