复习非限制性定语从句。
编稿：牛新阁审稿：王春霞。
概念引入。上一单元我们学习了限制性定语从句的有关知识，本单元将继续学习非限制性定语从句使用时注意事项以及作定语从句题的解题步骤等。
先看下面句子：
1. xie lei, who is 21 years old, has e to our university to study for a business qualification.
2. she is halfway through the preparation year, which most foreign students plete before applying for a degree course.
3. “you h**e to get used to a whole new of life, which can take up all your concentration in the beginning,” explained xie lei, who had lived all her life in the same city in china.
4. living with host families, in which there may be other college students, gives her the chance to learn more about the new culture.
5. cuzco is a lively city with many hotels and inns, where both indian and spanish culture and art can be seen.
这些句子中斜体词部分都是非限制性定语从句，有关系代词who/ which引导的，如句1、句2和句3；有介词+which引导的，如句4；也有关系副词引导的，如句5。另外as也能引导非限制性定语从句。那么用关系代词和关系副词引导定语从句有什么需要注意的呢？
as和which引导非限制性定语从句有什么区别呢？怎样做能把定语从句题都答对呢？下面我们就一一梳理学习。
用法讲解。两种定语从句。
1. 区别。
people who often take physical exercise live longer.
经常锻炼身体的人长寿。 (限制性：起限制作用，不能去掉)
his daughter, who is in boston now, is ing home next week.
他的女儿现在在波士顿，下周要回来了。（非限制性：补充说明，译成并列句）
2. 用非限制性定语从句的情况：
1）关系代词指代整个主句的内容。
she said she had finished her work, which i doubted very much.
她说她已经完成了这项工作，我对此深感怀疑。
2）先行词是世界上独一无二的事物或专有名词
the moon, which is 384,400 kilometers away from the earth, creates many beautiful stories.
月球，这个离地球384,400公里远的星球，给人们留下很多美好的故事。
3）先行词指的是某人的惟一某个亲属。
对比：his brother who is now a lawyer always encourages him to go to college. （限制性）
他那个现在是律师的哥哥总是鼓励他上大学。(他还有其他的哥哥)
his brother, who is now a lawyer, always encourages him to go to college. （非限制性）
他的哥哥，现在是律师，总是鼓励他上大学。(他只有一个哥哥)
4）“名词/代词/数词+介词+关系代词”结构中。
此结构常见的有：some (several, a few, many, most, part, the largest) of which/ whom等形式。有时of which/ whom可以提前到名词/代词等前。
i bought a dozen eggs, six of which (=of which six) broke when i dropped the box.
我买了一打鸡蛋，六个在我失手掉了盒子时摔碎了。
he went with a group of people, few of whom were correctly equipped for such a climb.
他和一队人一起去了，其中没有几个人配有进行这样一次登山的适当装备。
you’ve made many mistakes, most of which were due to your carelessness.
你犯了很多错误，大多数是由于你的粗心。
高清课堂：复习定语从句---which与as引导定语从句的区别】
which与as引导定语从句的区别。
. 限制性定语从句中。
限制性定语从句的先行词前有as, such, the same时，引导定语从句的关系代词用as不用which。例如：
1. there are as many dictionaries as are needed.
词典你需要多少有多少。
2. i h**e never heard such stories as he tells.
我从没有听过像他讲的这样的故事。
3. he is not such a man as i expected.
他并不是我期待的那样一个人。
4. we are facing the same problems as we did years ago.
我们面对着几年前（所面对的）同样的问题。
5. this is the same wallet as i lost. 这个钱包和我丢的那个一样。
注意：是否用as取决于先行词前是否有某些固定的词（as, such, the same）修饰。
. 非限制性定语从句中。
在非限制性定语从句中，as和which都可以表示一句话、一个整个的情况。
只放在主句后面，而as可在主句前，中，后。
as he realized, i was very useful to him. (在前)
正如他所认识到的那样，对他来讲，我还是能帮忙的。
air, as we know, is gas.（在中）
空气，就像我们知道的那样，是气体。
he is a foreigner, as i know from his accent. (在后)
他是外国人，我从他的口音中可以听出来。
2. as有“如同…… 正如……”的含义。
things will turn out contrary to one’s wishes, as is often the case.
结果往往与愿望是相悖的，正如经常发生的那样。
注意：下面这些从句，我们经常放在句首。
as we know我们都知道as has been said above/before 如上所述。
as has been pointed out 如上所述 as is known to all 众所周知 ■
from which还是from where
这是两个许多同学都困惑的结构，它们到底有什么区别呢？
1. from which用法比较好理解，可以引导限制性和非限制性定语从句。
there are several books about this on the shelf, from which i chose one and began to read it.
那个书架上有好几本有关的书，我选了一本开始读起来。
from which相当于and from the books）
2. from where常用于引导非限制性定语从句，在意义上相当于 and from there（从那儿）。
he hid himself in a tree, from where he could see the enemy in the distance.
他躲在一棵树上，从那儿他可以看到远处的敌人。（from where相当于from in the tree）
对比分析：he hid himself under the bed, from where he could hear what they were talking.
他躲在床下面，他可以从床下听到他们谈话。
分析：from where 可理解为 from under the bed，意思是“从床下面”。
但是：he hid himself under the bed, where he could hear what they were talking.
他躲在床下面，在床那儿他听到他们谈话。
分析：where可指为“在床边”“在床上”“在床下”等，意思不够明确。不能用from which。
定语从句的特殊结构。
一般定语从句紧跟着先行词，但实际运用时，具有较强的灵活性，下面是常见的特殊定语从句。
1. 分隔式：与先行词分离的定语从句。
the professor entered the hall who had just presented two lectures.
刚刚作完两场报告的教授走进了大厅。
2. 混杂式：
先行词后插入i think, i believe, i guess, i expect, i am sure, they say等。
james is the only one who we expect will win. 詹姆斯是我们认为唯一能获胜的人。
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