五、关系词—关系代词
1、He is a good student who studies hard.
2、He is a boy whom everyone loves.
3、He is a man for whom I enjoy working.（whom既不能做主语也不能做宾语，此时关系代词之前应置介词。）
关系代词之前有介词时，介词可移至引导的定语从句句尾，此时可省略关系代词。
He is a man I enjoy working for.
先行词为专有名词及独一性名词，如father、mother，之后若接关系代词引导的定语从句时，该关系代词之前一定要置逗号，此时该定语从句就称为非限制性定语从句。
He has just come back from New York， which is a very big city in the United States.
先行词为一般名词且本身并未具特殊性，可用定语从句加以限制，以加强其特殊性。限制性定语从句，将之译成“ … …的”，其关系代词前不置逗号。翻译时， 先译定语从句，再译先行词 。
He is a boy who works hard .
that也可当作关系代词，取代who、whom和which，但使用时有两个条件：
只能使用that的情况：
Gambling is the last thing that I would do.
He is the best student that I have ever seen in Guilin.
All that he said is true.
He 15 the only friend that I have.
He works hard , which is a fact that is known to us .
He is not the man that he once was.
Look at the boy and the dog that are coming this way.
限制性定语从句中，若 关系代词为主语时，该定语从句可化简为分词短语 。法则如下：
The girl who danced here yesterday is my sister.
The girl dancing here yesterday is my sister.
I like the car which is parked in front of the post office .
I like the car parked in front of the post office .
非限制性定语从句则 不能化简 。
关系代词所引导的定语从句中， 若该关系代词之前有介词时，可将该从句变换成不定式短语 。
He has no house in which he can live .
He has no house to live in .
我们曾在第一章谈到think 、believe 、feel、consider 、find等动词可作 完全及物动词或不完全及物动词 。
I think that he is nice.(完全及物动词)
He is a man who I think is nice.(此类动词属于插入语)
I think him to be nice.（不完全及物动词）
He is a man whom I think to be nice.(做不完全及物动词，此类动词不再是插入语)
