Hello大家好，今天我们来讲非限定性定语从句。有的小伙伴可能会有疑问，非限定性定语从句和我们之前讲过的定语从句有什么不同呢？先来一起来看看吧：
非限定性定语从句特点
1. 从形式上来说，非限定性定语从句有逗号；
2. 引导词来说：非限定性定语从句常见引导词是which，所指代和修饰的可以是主语中的名词，形容词，短语，其他从句或者整个主句。除了which之外，who，whom, whose, as 也可以引导非限定性定语从句
3. 含义上来说，非限定性定语从句是补充说明，拿掉不影响句子意思；限制性定语从句对名词起限定作用
大家整明白了之后，我们直接来练习一下看看~
首先，辨别非限定性定语从句我们可以通过句子中出现的逗号以及上述提到的常见的引导词 -- which来判断，这句话的主干成分与非限定性定语从句在哪里呢？
非限定性定语从句例句1:
He was nervous in front of so many people, which was understandable.
非限定性定语从句：which was understandable, 修饰he was nervous这件事
主干：He was nervous in front of so many people
其中，这句主干还涉及到了我们之后会讲的知识点 – 介词短语做修饰的情况，在把介词短语做修饰（in front of so many people）的成分去掉之后，主干就变成了he was nervous，更多介词短语相关的讲解，请大家拭目以待。
翻译：他以前在面对很多人的时候会很紧张，这是件很合理的事情
再来看一个句子吧～
非限定性定语从句例句2:
The council, which was founded in 1996, certifies fisheries that meet high environmental standards, enabling them to use a label that recognises their environmental responsibility.
比刚才的句子长了很多，但是解析句子的原理不变，来看下这句话的非限定性定语从句在哪里：
非限定性定语从句：which was founded in 1996, 补充修饰the council
主干：The council, certifies fisheries that meet high environmental standards, enabling them to use a label that recognises their environmental responsibility.
这句主干也涉及到了我们之前讲到的定语从句的知识点：
其中，that meet high environmental standards修饰fisheries；that recognises their environmental responsibility修饰a label.
把这些成分都去掉之后，主干变为：The council certifies fisheries, enabling them to use a label.
大家对非限定性定语从句有没有加深一点理解呢？更多练习可以移步到我们的赠送材料～
非限定性定语从句材料
先来复习一下知识点吧！
非限定性定语从句特点：
1. 从形式上来说，非限定性定语从句有逗号；
2. 引导词来说：非限定性定语从句常见引导词是which，所指代和修饰的可以是主语中的名词，形容词，短语，其他从句或者整个主句。除了which之外，who，whom, whose, as 也可以引导非限定性定语从句
3. 含义上来说，非限定性定语从句是补充说明，拿掉不影响句子意思；限制性定语从句对名词起限定作用
?先来看第一个句子：
首先先识别是否有非限定性定语从句做修饰的情况，然后再和主干区分开：
But the movies differed significantly from these other forms of entertainment, which depended on either live performance or (in the case of the slide-and-lantern shows) the active involvement of a master of ceremonies who assembled the final program.
通过标点符号以及关系词which的出现，我们可以比较容易的定位到非限定性定语从句的位置：which depended on either live performance or the active involvement of a master of ceremonies who assembled the final program.
主干：
but the movies differed significantly from these other forms of entertainment.
?再来看第二个句子：
Exhibitors, however, wanted to maximize their profits, which they could do more readily by projecting a handful of films to hundreds of customers at a time and by charging 25 to 50 cents admission.
还是通过标点符号以及关系词 – which的出现可以判定非限定性定语从句的位置：
Which they could do more readily by projecting a handful of films to hundreds of customers at a time and by charging 25 to 50 cents admission.
其中，这句话的非限定性定语从句中，又涉及到了介词短语做修饰的情况，把介词短语做修饰都去除之后，句子就被缩减为了which they could do more readily. 继续期待我们介词短语做修饰的讲解吧。
主干:
Exhibitors wanted to maximize their profits.
?来看下第三个句子：
先通过标点符号以及关系词 – who来确认非限定性定语从句做修饰在哪里
It was she, a Baltimore printer, who published the first official copies of the declaration, the first copies that included the names of its signers and therefore heralded the support of all thirteen colonies.
非限定性定语从句：who published the first official copies of the declaration, 修饰printer(she).
主干：
It was she, the first copies that included the names of its signers and therefore heralded the support of all thirteen colonies.
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