非限制性定语从句介绍
非限制性定语从句一般指非限定性定语从句。 定语从句有限制性和非限制性两种。下面是小编帮大家整理的非限制性定语从句介绍，供大家参考借鉴，希望可以帮助到有需要的朋友。
非限制性定语从句介绍
非限制性定语从句只是对主句内容，或先行词的补充、解释或附加说明。主句与先行词或从句之间一般用逗号分开，常常单独翻译。没有它，主句意思仍然完整。引导非限制性定语从句的关系代词有as，which，who， whom，whose等，作定语从句的主语、宾语、表语及定语。关系副词有when，where等，作定语从句的状语。关系代词和关系副词在定语从句中一般不能省。
一、as引导非限制性定语从句时，可以代主句的全部或部分内容。常表说话人关于说话的依据、态度、评论、看法等。有“正如、像”等意思。定语从句可以置主句句首、句中或句末。as后常接expect，know，report，say，see等动词的主、被动语态句。
1. ____is known to everybody，the moon travels round the earth once every month.
A.It B.As C.That D.What
2.Mike，as we expected，attended the meeting.像我们所期望的那样，迈克参加了会议。
3.He wasn't unconsicious，as could be judged from his eyes.他并未失去知觉，这从他的眼神可以判断出来。
二、which引导非限制性定语从句的情况很多。
I.指代主句的全部或部分内容时，常表事实、状态、起因等，有“这就使得、这一点”等意思，常置主句末。主句与定语从句用逗号分开。
1.Dorathy was always speaking highly of her role in the play，of course，madethe others unhappy.
A.who B.which C.this D.what
II.指代先行词有多种情况。定语从句置先行词后面。
1.在“n.／pron.／num....＋prep.＋ which”，“prep.＋which”定语从句里。 1）They talked about a movie，the name of which I've never forgotten.他们谈论过一部电影，我决不会忘记片名。
2）In Sydney the Chinese team got 28 gold medals，16.5 of which were won by women.在悉尼奥运会，中国队夺得了28枚金牌，其中16.5枚是女子夺得的。
3）China has thousands of islands，the largest of which is Taiwan.中国有数千个岛屿，其中最大的是台湾岛。
4）Chaplin went to the states in 1910，by which time he had learnt to dance and act in comedies.卓别林1910年去了美国，那时他已学会跳舞和演喜剧了。
2.表唯一性，或者就是指代先行词的事物时。
The dam，which is the biggest in the world，is 3，830 metres long.大坝长3，830米，是世界上最大的坝。
3.先行词是独一无二的'事物时。
The moon，which doesn't give out light itself，is only a satellite of the earth.月球本身不发光，它只是地球的一个卫星。
4.先行词表示类属的事物时。
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。
5.先行词是专有名词时。
1）Three of the biggest man-made projects in the world are the Great Wall of China，the Pyramids of Egypt and the Aswan High Dam， which is also in Egypt.世界上最大的三项人造工程是中国的长城，埃及的金字塔和阿斯旺高坝，它也在埃及。
2）The Nile，which used to flood every year，now runs more regularly below the dam.尼罗河年年涨洪水，现在比较正常地在大坝下面流过了。
6.先行词是表人的职业、品质、身份等名词，作定语从句的表语时。主句和定语从句之间含有对比的意思。
非限制性定语从句结构
who引导
Our guide，who was a French Canadian，was an excellent cook.
我们的向导，一个法裔加拿大人，擅长于烹调。
My gardener，who is very pessimistic，says that there will be no apples this year.
我家的园丁非常悲观，他说今年将不结苹果。
whom引导
关系代词whom用于指人，在句中作动词宾语和介词宾语，作介词宾语时，介词可位于句首。
如：Peter, whom you met in London, is now back in Paris.
彼得现在回巴黎了，你在伦敦见过他。
Mr Smith，from whom I have learned a lot，is a famous scientist.
史密斯先生是一位著名的科学家，我从他那儿学了许多东西。
whose引导
whose是关系代词who的所有格形式，在从句中作定语。whose通常指人，也可指动物或无生命的事物。
如：The boy, whose father is an engineer, studies very hard.
那位父亲是位工程师小男孩学习很努力。
Above the trees are the mountains, whose magnificence the river faithfully reflects on the surface.
在树林的高处是山，其壮丽的景色完全映照在河面上。
The play，whose style is rigidly formal，is typical of the period.
这剧本是那个时期的典型作品，风格拘谨刻板。
which引导
关系代词which在非限制性定语从句，中所指代和修饰的可以是主句中的名词、形容词、短语、其他从句或整个主句，在从句中作主语、动词宾语、介词宾语或表语。
① which指代主句中的名词，被指代的名词包括表示物、婴儿或动物的名词、表示单数意义的集体名词以及表示职业、品格等的名词。
如：These apple trees，which I planted three years ago，have not borne any fruit.
这些苹果树是我三年前栽的，还没有结过果实。
She is an artist，which I am not.
她是一位艺术家，而我不是。
Water，which is a clear liquid，has many uses.
水是一种清澈的液体，有许多用途。
The two policemen were completely trusted，which in fact they were.
那两个警察完全受到信任，事实上也确实如此。
② which指代主句中的形容词。
如：She was very patient towards the children，which her husband seldom was.
她对孩子们很耐心，她丈夫却很少这样。
She is always careless，which we should not be.
她总是马虎大意，我们可不应该这样。
③ which指代主句中的某个从句。
如：He said that he had never seen her before，which was not true.
他说以前从没见过她，这不是真的。
④ which指代整个主句。
如：In the presence of so many people he was little tense, which was understandable.
在那么多人面前他有点紧张，这是可以理解的。
He may have acute appendicitis，in which case he will have to be operated on.
他可能得了急性盲肠炎，如果是这样，他就得动手术。
When deeply absorbed in work，which he often was，he would forget all about eating and sleeping.
他经常聚精会神地工作，这时他会废寝忘食。
when引导
关系副词when在非限制性定语从句中作时间状语，指代主句中表示时间的词语。
如：He will put off the picnic until May 1st, when he will be free.
他将把郊游推迟到5月1号，那时他将有空。
where引导
副词where在非限制性定语从句中作地点状语，指代主句中表示地点的词语。
如：They went to London，where they lived for six months.
他们去了伦敦，在那儿呆了六个月的时间。
as引导
as引出非限定性定语从句时，代替整个主句，对其进行说明但通常用于像as we all know, as it is known, as is known to all, as it is, as is said above, as always mentioned above, as is usual, as is often the case, as is reported in the newspaper等句式中。as在非限定性定语从句中作主语、表语或宾语，且引出的从句位置比较灵活，可位于句首或句末，也可置于主句中间。通常均由逗号将其与主句隔开。as有“正如……， 就像……”之意。
如：As is known to the United States, Mark Twain is a great American writer.
美国人都知道，马克·吐温是一位伟大的美国作家。（as在从句中作主语）
He forgot to bring his pen with him, as was often the case.
他忘了带笔，这是常事。（as在从句中作主语）
He is absorbed in work, as he often was.
他正在全神贯注地工作，他过去经常这样。（as在从句中作表语）
As we all know, the earth is round.
众所周知，地球是圆的。（as在从句中作宾语）
The two brothers were satisfied with this decision，as was agreed beforehand.
两兄弟对此决定都满意，这项决定在事前都已得到他们的同意。(as在从句中作主语)
Taiwan is，as you know，an inseparable part of China.
你知道，台湾是中国不可分割的一部分。(as在从句中作宾语)
“介词+关系代词”引导非限制性定语从句：在介词后引导非限制性定语从句。
难：句意相同
as it is known to all (that...) (as 做状语从句连词，是状语从句, 可以加that)
与 as is known to all (as做主语，是定语从句)
与 it is known to all that... (主语从句，it是形式主语)
即：As is widely known, the moon is closer to the us than the sun.(定从)
= That the moon is closer to the us than the sun is widely known.(主从)
= It is widely known that the moon is closer to the us than the sun.(主从)
As it is known to everyone, I thought you knew about it too.(状从)
关系代词which有时并不代表主句中某一确定的词，而是概括整个主句的意思。介词的选择取决于它与先行词的搭配或与从句中谓语动词的搭配。
They were short of sticks to make frames for the climbing vines，without which the yield would be halved.
他们缺搭葡萄架的杆儿，没有它们产量会减少一半。
They thanked Tom，without whose support they would not have succeeded.
他们很感激Tom，没有他的支持他们是不会成功的。
特殊结构
“名词/代词+of+which / whom”
It now has 20，000 hectares of land，more than two-thirds of which are under cultivation.
现在它拥有两万公顷土地，其中三分之二之多已经耕种。
Light is the fast thing in the world, the speed of which is 300000 kilometer per second.
光是世界上最快的东西，它的速度是每秒30万千米。
There are 30 chairs in the small hall, most of which are new.
大厅里有三十把椅子，绝大部分是新的。
The textile mill has over 8，000 workers and staff，eighty per cent of whom are women.
这家纺织厂有8千多职工，女职工占百分之八十。
限制性定语从句与非限制性定语从句的区别
区别一：形式不同
限定性定语从句主句和从句之间不用逗号隔开，口语中使用时也不停顿;而非限定性定语从句与主句之间通常有逗号隔开，口语中使用时有停顿。
区别二：功能不同
限定性定语从句用于对先行词的意义进行修饰、限制和识别，如果去掉，就会造成句意不完整或概念不清;而非限定性定语从句用于对先行词起补充说明作用，如果省略，句意仍然清楚、完整。如：
People who take physical exercise live longer. 进行体育锻炼的人活得长些。（若把从句去掉句子就失去意义）
His daughter， who is in Boston now， is coming home next week. 他女儿现在在波士顿，下星期回来。（若把从句去句子意义仍然完整）
区别三：翻译不同
在翻译定语从句时，一般把限定性定语从句翻译在它所修饰的先行词之前，而把非限定性定语从句与主句分开。如：
He is the man whose car was stolen. 他就是汽车被窃的那个人。
I’ve invited Jim， who lives in the next flat. 我邀请了吉姆，他就住在隔壁。
区别四：含义不同
比较下面的两个句子：
I have a sister who is a doctor. 我有一个医生的姐姐。（姐姐不止一个）
I have a sister， who is a doctor. 我有一个姐姐，她是当医生的。（只有一个姐姐）
区别五：先行词不同
限定性定语从句的先行词只能是名词或代词，而非限定性定语从句的先行词则可以是名词或代词，也可以是短语或句子;另外，当先行词为专有名词或其他具有独一无二性的普通名词时，通常要用非限制性定语从句，而不用限制性定语从句。如：
Peter drove too fast， which was dangerous. 彼得开车很快，这是很危险的。（which指drive too fast）
He changed his mind， which made me very angry. 他改变了主意，这使我很生气。（which指整个主句）
Mr. Smith， who is our boss， will leave for Japan next week. 我们的老板史密斯先生下周要去日本。（先行词为专有名词，要用非限制性定语从句修饰）
区别六：关系词不同
关系词that和why可用于限制性定语从句中，通常不用于非限制性定语从句;另外，在限制性定语从句中，关系词有时可以省略（参见本章有关内容），而在非限制性定语从句中关系词一律不省略。
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