先来看一个句子：

正如我们所知道的，有些话题可能比较敏感，比如宗教或政治。

As we all know， some topics can be touchy， like religion or politics.

上面的句子中就包含一个非限制性定语从句。那么，什么是限制性定语从句和非限制性定语从句呢？

1.定语从句

限制性定语从句

非限制性定语从句

2.限制性定语从句

对先行词的意义进行修饰、限制和识别。如果去掉，会造成句意不完整或概念不清。主句和从句之间不用逗号隔开，口语中不停顿

I don＇t like people who are never on time.

我不喜欢不守时的人。

3.非限制性定语从句

提供附加而非必要的信息，只是对先行词做进一步解释、说明或补充。如果省略，主句的意义一样明确，不会引起误解和歧义。从句与主句之间通常有逗号隔开，口语中有停顿。

My mother， who is 86， lives in Beijing.

我母亲，86岁了，住在北京。

4.翻译方式不同

限制性定语从句，一般翻译为前置定语，译为……的。非限制性定语从句，一般将主句和从句译成两个并列部分。

I have a sister who is a doctor.

我有一个做医生的姐姐。

I have a sister， who is a doctor.

我有一个姐姐，她是当医生的。

5.所修饰的先行词通常不同

①限制性定语从句的先行词只能是名词、代词或短语，而非限制性定语从句的先行词可以是名词、代词、短语或句子。

The boy who was in the office yesterday is my brother.

昨天在办公室的那个男孩是我弟弟。

He changed his mind， which made me very angry.

他改变了主意，这使我很生气。

②先行词为专有名词时，通常使用非限制性定语从句，起进一步解释、说明或补充作用。

Beijing， which is the capital of China， has developed into an international city.

北京，中国的首都，已经发展成为了一个国际化都市。

6.关系词有所不同

①限制性定语从句中，关系词作宾语时，可省略；非限制性定语从句中，不可省略。

Who＇s that man he＇s talking to？

跟他说话的人是谁？

He had new girlfriend， whom he wanted to impress.

他新交了一个女朋友，想给她留下深刻印象。

②that可引导限制性定语从句，但通常不引导非限制性定语从句。

My friend bought me his book， which I still haven＇t read.

我的朋友给我买过他的书，不过我还没看。

7.关系代词as和 which

①表达意思不同

1）as引导的定语从句表示说话人对话语的看法、态度、依据、解释或评论，译为正像

As was expected， the answers were the same.

不出所料，答案是一样的。

2）which引导的定语从句，是对主句所叙述的事情进行补充说明，说明事物的状态或结果，如果需要，可翻译为这一点

Claire is a perfectionist，which sometimes is a good thing.

克莱尔是个完美主义者，这有时候是好事。

3）主句和从句在内容上不一致，或从句内容对主句内容起反对、排斥、否定等作用时，通常使用which，不用as

She has married again， which was unexpected.她又结婚了，这真出乎人们预料。

She has married again， as was expected.

她又结婚了，正如人们预料的那样。

②位置不同

1.as引导的定语从句位置较灵活，可放在主句之前、之中、之后，一般用逗号和主句隔开

As is known to all， the Pacific is the largest ocean.

The Pacific， as is known to all， is the largest ocean.

The Pacific is the largest ocean， as is known to all.

众所周知，太平洋是最大的洋。

2）which引导的定语从句一般放在主句之后

The road was too slippery， which caused lots of accidents.

路太滑，引起了很多事故。

练习：

一、单句改错。

1. When people talk about Hangzhou, the first comes to mind is the West Lake.

2. In the distance there is a hill, on the top of it stands a white temple.

3. I have never been to Dalian which is said to be an attractive city.

4. The sun gives off light and warmth, that makes it possible for plants to grow.

5. In an open boat, the four men, one of them was a doctor, met with a storm on the sea.

二、用适当的关系词填空。

1. The leader of the team is a 44-year-old Frenchman, ________ wife is also a team member.

2. He reached London in 1996,________ , some time later, he became a famous actor.

3. Mr Green will come to the party on Sunday, ________ he promisedto every one of us.

4. The professor has two sons, both of ________ are teaching in the same university.

5. The film brought the hours back to me ________ I was taken good care of in that far away village.

三、把下列汉语翻译成英语。

1． 汤姆努力学习并乐于助人，这正是他父母所期盼的。

2． 他们将乘飞机去昆明，在那里他们将呆两三天。

3． 老人有两个女儿，其中一个是医生。