限制性定语从句与非限制性定语从句
1．限制性定语从句说明先行词的情况，对先行词起限定作用，与先行词关系十分密切，不可用逗号隔开，也不可省略，否则全句意义就不完整。如：This is the telegram which he refers to.
Is there anything (that) I can do for you?
2．非限制性定语从句只是对先行词作补充说明，没有限定作用，它与先行词的关系比较松散，因而不是关键性的，如果省略，原句的意义仍然完整。This note was left by Tom, who was here a moment ago.
As a boy, he was always making things, most of which were electric.
引导非限制性定语从句的关系词有：who, whom, whose, which, when 和where，不可以用that和why。
3．两种定语从句的内涵不同，限制性定语从句具有涉他性，而非限制性定语从句具有唯一性，这在理解和翻译时应特别注意。试比较：
All the books there, which have beautiful pictures in them, were written by him. All the books there that have beautiful pictures in them were written by him.
His brother, who is eighteen years old, is a PLA man. （只有一个）
His brother who is a PLA man is eighteen years old. （不止一个）
4. that 不引导非限定性定语从句.
5．有时，非限制性定语从句所修饰的不是某一个词，而是整个主句或是主句中的一个部分，这时一般采用which或as来引导。如：
He passed the exam, which/as he hoped.
注：（1）as引导的从句既可以放在主句之前又可以放在主句之后，而which 引导的从句只能放在主句之后。
They are hollow, which makes them very light.
As is known to all, Taiwan is a part of China.
（2）从意义上讲，which指前面主句的内容，常译成“这，这件事”；而as 指代的是作为一般人都知道的常识性的东西，因此常译成“就象…那样，正如…”
（3）as 在定语从句中可做主/宾/表，而which通常做主语
As we can see/ As can be seen, he is a good student.
He tore up my photo, which upset me.
练习：用关系代词和关系副词填空。
1.______ is expected, the England team won the football match.
2. The earth runs around the sun, ______ is known by everyone.
3. He is often late, ______ is known to all.
4. ______ you know, this is the day the quake happened.
5. Jack came late for school, ______ made his headmaster angry.
6.He is working hard，______will make him pass the final exam.
7. She changed her mind again, ______ made us all angry.
8. The honest boy told a lie, ______ he found strange.
9._____ is reported in the newspapers, they have beaten all the other teams.
10.______has been said above, grammar is a set of dead rules.
11.____________________(正如经常发生的那样)，LiuXiang won the gold medal again.
12._____________________（正如被期盼的那样），LiuXiang won the gold medal again.
13.______________________(众所周知)，the year 1976 saw a big earthquake in Tangshan.
14. He failed in the exam, _______made his parents angry.
15. John said he’d been working in the office for hours, ______ was true.
16. He wrote the best composition, ____ surprised all of us.
17. The doctor advised Vera strongly that she should take a holiday, ____ didn’t help.
18. The result of the experiment was very good, ______ we hadn’t expected.
19. The crops were badly damaged by the storm, ________did damage to the income of the local farmers.
20. He is working hard, ______will make him pass the final exam.
21. The settlement is home to nearly 1,000 people, many of _____left their village homes for a better life in the city.
22. She brought with her three friends, none of _____I had ever met before.
