一. 非限制性定语从句与主句的关系
非限定性定语从句是对主句或主句中的主语或宾语进行信息的补充、说明而不是真正意义上的起修饰或限制作用。所以就其和主句的关系而言不像限定性定语从句与主句那么密切，紧凑，从而显得松散。在文章中它所提供的信息往往是辅助性信息，是细节，而非主要信息。逗号“，”的使用正是书面语中这种关系的体现，也成了我们判断限制性定语从句和非限制性定语从句的一个明显的标志。
因此，非限制性定语从句只是形式上的主句的修饰成分，但实质上它却有着与主句各种各样内在的意义上的逻辑关系。
The sun heats the earth , which makes it possible for plants to grow . 太阳给予大地热，这就使植物的生长成为可能。
Rockets perform best in space, where there is no atmosphere to impede their motion. 火箭在太空中运行最佳，因为在那儿不存在阻碍他们运动的大气。
分析：在语义上，定语从句与主句的关系为因果关系，因此我们将定语从句译成原因状语从句。 I told the news to Robert，who told it to his friend Larry，and soon the news spread all over the campus. 我把消息告诉了罗伯特，他又告诉了他的朋友莱里，消息很快在校园里传开了。 分析：who引导的非限制性定语从句很显然存在着逻辑上的并列关系。 My uncle，who will be seventy tomorrow，is still a keen sportsman. 尽管我大伯明天就满70岁了，但他仍然热衷于户外运动。
分析：很明显，用非限制性定语从句交待“My uncle will be seventy tomorrow”这一额外信息就是为了呼应“still a keen sportsman”。所以本句可改写成一个让步主从句： Though he will be seventy tomorrow，my uncle is still a keen sportsman.
总之，非限制性定语从句与先行词之间的关系比较松散，和主句之间逻辑上存在着明显的状语关系，说明时间、原因、条件、目的、结果或让步等。它不是先行词的不可缺少的组成部分，只是对先行词作进一步说明，作为补充而已。书写时要用逗号隔开，在口语中有停顿。如果省略，并不影响先行词的所指意. 真题赏析：
1. The famous basketball star, ___ tried to make a comeback, attracted a lot of attention. (02安徽春季) A. where B. when C. which D. who 因果关系：可改写成“Because the famous basketball star tried to make a comeback, he attracted a lot of attention.”
2. I walked in our garden, ____Tom and Jim were tying a big sign onto one of the trees. (05辽宁卷) A. which B. when C. where D. that 时间状语关系：可改写成“I walked in our garden while Tom and Jim were tying a big sign onto one of the trees.”
3. Anyway, that evening, ___ I’ll tell you more about later, I ended up staying at Rachel’s place. (04浙江) A. when B. where C. what D. which 转折关系：可改写成“Anyway, that evening I ended up staying at Rachel’s place, but I’ll tell you more about later.” 1 二．非限制性定语从句的使用
英语阅读或作文中，非限制性定语从句的功能以及句式解构特点决定了该句式为高频句式。一方面它提供了丰富的信息增加了句子的信息含量，另一方面增强了句子的逻辑性。作文中恰当使用非限制性定语从句无疑使句式富有表现力，也是驾驭英语语言的一个具体表现。但初学者总是在一定的语境下该不该使用非限制性定语从句而犹豫不决，有的在使用时把限制性定语从句和非限制性定语从句混为一谈。其实，使用时我们还是从它们的功用出发进行推敲判断，不难发现如下规律：
1. 对人们所熟知的人和事物进行描述时，往往用非限制性定语从句。
1）Beijing, which is the political and economic center of China, lies to the west of the city of Tianjin. 北京位于天津西面，是中国的政治文化中心。
2）Football，which is a very interesting game，is played all over the world． 足球是一项非常有趣的运动, 全世界都踢足球。
3) Spielberg, whose mother was a music teacher, was born in 1946 in a small town in America. 斯皮尔博格于1946年出生在美国的一个小镇，他的母亲是一位音乐教师。
我们稍做分析就会发现，以上非限制性从句的先行词是北京、足球、和斯皮尔博格，这些词虽然有人物也有地名，但都有一个共性，就是：他们都是一说大家都知道的，给读者的信息是清楚明确的，所以没必要再对他们进行修饰限制。
2. 对其不熟但具有唯一性的人或事物进行描述时，常用非限制性定语从句。
1）His mother, who was a common and hard-working Chinese woman, died 20 years ago, leaving five of them children.
他的母亲是一位普普通通，勤劳的中国妇女，她是20年前去世的，留下他们5个还未成年的孩子。
2）Xiao Wang, who saved a drowning child last month, was honored by the local government. 小王救了一位溺水儿童，受到当地政府的表彰。 在这两个句子中，都使用了非限制性定语从句，就说明了母亲和小王在作者和读者心中的唯一性。生母就一个这是不言自明的事。如果在例1）中使用了限制性定语从句，读者会认为他不止一个母亲，可能会闹出笑话。例2）也是如此。
3. 对前面整句话进行信息补充时，常用非限制性定语从句。
1）Peter drove too fast, which was dangerous. 彼得开车很快，这是很危险的
2）He changed his mind, which made me very angry. 他改变了主意，这使我很生气。
其实，这样一种句式结构是非限制性定语从句的一大特色，起到补充细节的作用，一般位于主句的后面，在逻辑上表目的，结果等。在高中英语给要点写作中适当添加细节常用句型。 三. 非限制性定语从句的关系词。
限制性定语从句的关系词有：that, which, who(m), whose, when, where, why, as 而非限制性定语从句关系词有：which, who(m), whose, when, where, as 其中that和why不引导非限制性定语从句；且引导非限制性定语从句的关系词即使在从句中作宾语也不能省略。
1）which 在引导非限制性定语从句除了指代主句的代词或名词，还可指代前面整个句子。 Jim passed the driving test, _____surprised everybody in the office. (05浙江)
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A. which B. that C. this D. it
Dorothy was always speaking highly of her role in the play, ____, of course, made the others unhappy. ( 00全国卷)
A. who B. which C. this D. what
2）as也是非限制性定语从句的常用关系词，有着和关系词“which”一样的功能：可指代整个句子，其引导从句的位置常在主句的前面, 亦有置于主句中，后的情况但常是肯定语气，意为“正如„”。
Mike, as we expected, attended the meeting．我们所期望的那样，迈克参加了会议。
____ is reported in the newspapers, talks between the two countries are making progress. (04北京卷) A. It B. As C. That D. What
____ is known to everybody，the moon travels round the earth once every month． A. It B. As C. That D. What
3)“介词+ which\\ whom” 和 “介词+ when\\ where”引导的非限制性定语从句
这里的介词均来自于体现上下文逻辑关系的短语里。比如：：in that\his case, at this\his point, at\\during that time, by that\his time, after that, since then, with\\without one's help, （prep + one's + n.), as a result of., for sb\\ sth等。
1. It rained all day and all night, ____ time the ship broke in pieces. A. for which B. at which C. when D. during which析：先行词all day and all night是具体的时间，time概念涵盖先行词，应选择D。（分解后的句子应是：It rained all day and all night. During that time, the ship broke in pieces.)
2. We came back on Tuesday, since when we have been working in the repair shop. (我们星期二回来，从那时起就一直在修配间工作。) ( 分解后的句子应是: We came back on Tuesday,. Since then , we have been working in the repair shop.)
4. His head soon appeared out of the second storey windows，from where he could see nothing but trees．
他的头很快从第二层楼的一个窗户伸出来了，从那里他只能看见树木。 5.I went to bed at ten，before when I was reading for an hour． 我10点去睡觉，在那时以前我看了1小时的书。
I finished my work ahead of time, after which I sat some time reading the newspaper 我提前干完了我的活，随后我坐着看了一会儿报纸。
【注意1】有时候where ／when可以用prep + which替换。
6. The southern states wanted to set up a country of their own，in which/where they would be free to keep black slaves．
南方各州要建立一个属于他们自己的国家，在那里他们将自由地保留黑人奴隶。 7.I still remembered January 10，on which／when he came to see me． 我仍然记得1月10日，那一天他来看我了。
【考例】Ba Jin, for __ experiences were adventurous and unforgettable, was an old man always telling the truth. A. whom B. whose C. that D. which 答案：A 【注意2】虽然非限制性定语从句不能用why引导，但可用for which代替why。如：
3 8. I had told them the reason, for which I didn't attend the meeting. 我已经把理由告诉了他们，为此我没有去开会
4) whom 引导的非限制性定语从句中，whom不能用who取代，也不能省略。 1. Do you know Tom, whom we talked about? 你认识汤姆吗? 我们谈到过他。 四、转化
非限制性定语从句 与非谓语动词（短语）
1. Tom was always late for school, which made his teacher angry.
= Tom was always late for school, making his teacher angry. 【现在分词作结果状语】
2. The Great Wall, which is called in Chinese “The Ten-Thousand li Great Wall”, is actually more than 6,000 km.
= The Great Wall, which is called in Chinese “The Ten-Thousand li Great Wall”, is actually more than 6,000 km. 【过去分词作定语】
3. English is a language shared by several diverse cultures, each of which uses it somewhat different. 【2011浙江卷】
= English is a language shared by several diverse cultures, each of them using it somewhat different.【独立主格结构】
非限制性定语从句 与主语从句
1. The air quality in the city, _______ is shown in the report, has improved over the past two months. 【2012福建卷】 A. that B. it C. as D. what
= As is shown in the report, the air quality in the city has improved over the past two months.
= What is shown in the report is that the air quality in the city has improved over the past two months. 【主语从句、 表语从句】
= It is shown in the report that the air quality in the city has improved over the past two months. 【主语从句】
通过句型转化，我们可以看出：学习定语从句时，尤其非限制性定语从句，我们不应该拘泥于从句本身，而是开阔思路，仔细揣摩，领悟语言内在规律性，真正做到举一反三，触类旁通，这样驾驭语言本领自然水到渠成。
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