下面是小编整理的as, which 非限定性定语从句的用法（共含7篇），希望能帮助到大家!同时，但愿您也能像本文投稿人“亘谷网络运营”一样，积极向本站投稿分享好文章。
由as, which 引导的非限定性定语从句，as和which可代整个主句，相当于and this或and that。As一般放在句首，which在句中。
As we know, smoking is harmful to one's health.
The sun heats the earth, which is very important to us.
典型例题
1)Alice received an invitation from her boss, ___came as a surprise.
A. it B. that C. which D. he
答案C. 此为非限定性从句，不能用 that修饰，而用which.，it 和he 都使后句成为句子，两个独立的句子不能单以逗号连接。况且选he句意不通。
2)The weather turned out to be very good, ___ was more than we could expect.
A. what B. which C. that D. it
答案B。which可代替句子，用于非限定性定语从句，而what不可。That 不能用于非限定性定语从句，it不为连词，使由逗号连接的两个句子并在一起在英语语法上行不通。
3)It rained hard yesterday, ____ prevented me from going to the park..
A. that B. which C. as D. it
答案B.
as 和which在引导非限制性定语从句时，这两个关系代词都指主句所表达的整个意思，且在定语从句中都可以作主语和宾语。但不同之处主要有两点：
(1) as 引导的定语从句可置于句首，而which不可。
(2) as 代表前面的整个主句并在从句中作主语时，从句中的谓语必须是系动词;若为行为动词，则从句中的关系代词只能用which.。
在本题中，prevent由于是行为动词，所以正确选项应为B。
As 的用法
例1. the same… as;such…as 中的as 是一种固定结构, 和……一样……。
I have got into the same trouble as he (has).
例2. as可引导非限制性从句，常带有'正如'。
As we know, smoking is harmful to one's health.
As is know, smoking is harmful to one's health.
As是关系代词。例1中的as作know的宾语;例2中，它充当从句的主语，谓语动词know要用被动式。
定语从句why的用法：
关系副词why在定语从句中也是用作状语，表示原因;why引导定语从句时，其先行词只有一个，那就是the reason;在许多情况下why也可以理解为for which。如：
These are the reasons why we do it. 这些就是我们这样做的`理由。
句中的why we do it为修饰the reason的定语从句，关系副词why在此相当于for which。
Do you know the reason why she doesn’t like me? 你知道她不喜欢我的原因吗?
句中的why she doesn’t like me为修饰the reason的定语从句，关系副词why在此相当于for which。
why是一个比较特殊的关系副词，它引导定语从句时，除可换成for which外，有时也可换成that，甚至省略。如：
他失去工作的主要原因是他喝酒。
正：The main reason why he lost his job was that he drank.
正：The main reason for which he lost his job was that he drank.
正：The main reason that he lost his job was that he drank.
正：The main reason he lost his job was that he drank.
Tankfield emailed Pea some photos, which Pea did not find interesting.
which就近指代photos，photos是定语从句中的宾语，把定语从句还原成一个完整句就是Pea did not find the photos interesting.
可以看到，上面两个句子都可以以that为关系代词改写，即
(1)Tankfield emailed Pea some photos that did not cheer Pea up.
(2)Tankfield emailed Pea some photos that Pea did not find interesting.
which前面是介词，介词前面是名词，which就近指代介词前的那个名词，名词和介词之间有无逗号均可。
Tankfield once lent Pea a book from which Pea glimpsed the basics of genes.
这个句子可以“拆”成如下两句：（每个定语从句都可以拆成两句，以先行词为拆分点）
(1)Tankfield once lent Pea a book.
(2)Pea glimpsed the basics of genes from the book.
先行词实际上是定语从句中介词的宾语，这时，需要把介词提前，避免如下表达：
(1)Tankfield once lent Pea a book, which Pea glimpsed the basics of genes from. (XXX)
(2)Tankfield once lent Pea a book that Pea glimpsed the basics of genes from. (XXX)
上中学的`时候学过，which引导的定语从句叫“非限制性定语从句”，是不是？它怎么就“非限制性”了？回顾上述GMAT语法规定which有且仅有的两种用法，which指的都是就近的名词，从句其实还是限制性的。
所谓非限制性呢，是说which指逗号之前一套主谓所描述的情况，以逗号前的一个完整句为先行词。比如：
(1)Tankfield might never care to say Happy Birthday to Pea, which was rather sad.
(2)Tankfield might never care to say Happy Birthday to Pea, which Pea did not refuse to acknowledge to herself any more.
只是补充、进一步附加说明先行词的内容，有时是对前面整个英语句子的情况给予补充说明。
所以，即使删除了非限制性定语，并不影响句子意思的表达，只是少了一点补充或附加信息而已。
由于非限制性定语从句与先行词的关系不那么密切，一般可以用逗号将它们分开来。
例如：
She wants a pet, which can keep her company every day.
她们想要一只宠物，每天都能陪伴她。
(并没有限定什么样的宠物，该句的非限定语从句只是附加说明她养宠物的作用，即使删除，剩下she wants a pet.意思也是表达完整的。)
注意：
非限定性定语从句并不总是修饰一个先行词，有进还可以修饰它前面的的整个主句或者主句中的一部分。
例如：
The lady persuaded the boy to let the bird go, which made her extremely happy.
女士说服小男孩把鸟放掉了，这使她感到极为开心。
(非限制性定语从句修饰前面整个主句。)
Lily got to know that she passed the mathematical test, which set her heart at rest at last.
莉莉获知她已经通过了数学考试，这使她终于放心了。
(非限制性定语从句修饰hepassed the mathematical test 这部分内容。)
限制性定语从句和非限制性定语从句不仅在关系代词使用和先行词的关系上有差异，有时在意思上也有比较大的差别。
例如：
Now we have 5 classes which learn English.
现在我们有5个学英语的班。
(暗含“我们的班不只5个，别的班不学英语”之意。)
In our school there were one hundred students, who could sing English songs very well.
在我校当时有100学生，他们都很会唱英文歌。
(表明“我校当时只有100个学生”。)
作者|丹丹英语
公众号：英语语法学习
本文已获授权，版权归作者所有，如需转载，请联系原微信公众号“英语语法学习”
In our school there were one hundred students who could sing English songs very well.
在我校当时有100学生很会唱英文歌。
(表明“我校当时不止100个学生，其他学生不太会唱英文歌”。)
★ 定语从句
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★ 中考定语从句教案
★ 定语从句翻译句子
