定语从句:包含主语谓语起修饰名词作用的句子叫定语从句
定语的成分：
1.形容词作定语
a beautiful lady
2.名词作定语
the daughter of the professor ， the book of a boy or a boy's book
3. 介词短语
the boy out of the window
a boat in the sea
4.分词、不定式
the singing girl
a dancing boy
a boy cheated by a girl
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定语的位置
一般来说，单个词作定语放在被修饰词前面，而多多个词或从句作定语放在后面，但是过去分词作定语，放在后面。
This is a story about a rose and a boy介词短语，较长放后面
At the party, the young boy understanding romance was rejected 现在分词短语作定语，放在后面
the boy dumped looks pitful 过去分词作定语放在后面
定语从句的引导词根据词性本身可以分为三类
1.代词 （在从句中充当主语和宾语）who（可做主语和宾语） whom（宾语） that which
Do you know who did this
Do you know whom I spend last night with?
2.副词 （在从句中补充当任何成分） where when why
I never forget the day when we met
I do not know why she went away
Life is like a long race where **we can go beyond ourselves by competing with others. **(从句不缺主谓宾，引导词为副词)
3.形容词（在从句中只充当定语修饰名词）whose
He is the man whose father is wealthy
I love buildings whose roofs are round
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定语从句中的引导词是关系代词，相当于连词和代词，由于代词分为主格、所有格、宾格，所以关系代词也有主格、所有格、宾格之分。注意：区别名词性从句，“其that引导词在从句中不做任何成分”。
1.主格关系代词 who
Do you know the girl who played the piano？
I have an uncle who lives far away
2.所有格关系代词 whose
I have a friend whose name is Lucy
I met a woman whose husband is a teacher
3.宾格关系代词
I love the girl whom/who I met yesterday（met 及物需要宾语，这里whom 作met的宾语）
关系代词
1.which 当先行词为事情或物的时候，其也分为主格、宾格、和所有格
1.主格：
This is the book which is very interesting （先行词事物）
I like the cat which has blue eyes （先行词动物）
2.所有格：先行词是人或物是的都只能用whose
This is the table whose leg was broken yesterday
I love the cat whose hair is black
3.宾格：
This is the car which I bought yesterday
省略关系代词情况：
1.只有宾格的关系代词可以省略，其他不可以
I know the who loves you. who作主语不能省略
I know the man (whom/who) you love. whom/who作宾语可以省略
2.“主格关系代词+be动词+分词（过去分词和现在分词都可以） ”可以 省略 “主格关系代词+be”：
1.现在分词
The boy who is standing by the door is my brother
The boy standing by the door is my brother
2.过去分词
I received a letter which was written in English
I received a letter written in English
介词+关系代词
which 引导定语从句可以把介词提前放在which前面，这里which是介词宾语不能省略，如下面两个句子
This is the desk which I put my bag on （which 可以省略）
This is the desk on which I put my bag （which 不可省略）
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关系代词 THAT
That 是无论先行词是什么（人或者物）都可以用的一个关系代词，但是如果是所属格要用whose 或者of which，
I have an uncle who/that lives in China
This is a watch that/which made in Korea
This is a singer whom/who/that I want to see
只用which 不用that
介宾引导的定语从句不能用that
This is the house in which I live
非限制性定语从句（除了不能用that也可以用其他的词引导 ）
I like the cat，which is beautiful
I like Mrs. Liu，who is very charmful
He went to America，where the war broke out
She went to the house，where she could not see him
先行词只能用that的情况
1.人+事物一起存在
Look at the dog and her dog that are running
2.先行词是the+最高级或者the+序数词
She is the tallest girl that I have ever seen
Jane is the first girl thatcame to the school
3.先行词有all，every，some，any，no时候
Everyone that goes to the school looks happy
All that glitters is not gold
4.先行词有the very， the only，the same时候
This is the same/very watch that I lost yesterday
5.先行词有who，which 时候
Who that knows him will trust him
Which of the movie that you watched this year is the tbest？
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名词性代词和关系代词that区别
1.看that后面是不是完整的句子
It is true that I helped him yesterday（that 后面主谓宾都有）名词性从句
This is Shrek that married Fiona （that作主语且前面有先行词）定语从句
2.看that 前面有没有先行词
I didinot know that he was a singer （that 前没有先行词）名词性从句
He is the most clever guy that I have ever seen （that 前有先行词）定语从句
What代替先行词+关系代词
I understand the thing which you said
I understand what you said
这里的what=thing which
I know the thing which you did last month
I know what you did last summer
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除了关系代词可以引导定语从句，“关系副词” 也可以引导定语从句，同时起着 “连词和副词” 的作用
“介词+关系代词”可以用“关系副词”进行替换
This is the place in which I was born
This is the place where I was born
关系副词的种类
1.Where（先行词表示场所）
This is the place where I was born (I was born 是完整句子)
We went to the place where we were able to camp （we were able to camp也是完整句子）
也就是说关系副词引导定语从句，从句是完整句子
New York is a city where the UN members meet = New York is a city in which the UN members meet
This is a place which I want to visit is beautiful （visit is 及物动词）
The place where I want to go is beautiful （go 不及物 ）
2. When（先行词表示时间）
I remember the day which she was born on
I remember the day on which she was born
I remember the day when she was born
这里 on which 可以用when 代替
3. Why（先行词表示理由）
This is the reason which he was late for
This is the reason for which he was late
This is the reason why he was late
这里for which 可以用why代替
4. How（先行词表示方法）
This is the way in which she solved the problem
This is the way how （that） she solved the problem
由于the way 是方法 how也是方法，，所以这里有些重复，去掉the way即可 或用关系‘副’词that
This is how she solved the problem
参考《不就是语法和长难句吗》和《英语分解语法大全》