非限制性定语从句语境呈现1观察下列句子，注意划线部分的用法。
1)This note was left by Mr.Li,who was here a moment ago.2)This novel,which I have read three times,is very touching.3)The bus ran into a crowd of people,some of whom were sent to hospital.4China has hundreds of islands,the largest of which is Taiwan.5)She was kinder to her youngest son than to the others,which,of course,made the others envy him.6)All of my books are on the desk,where I always keep them.7)My brother,whose skin is a little black,has a slim figure.8)They decided to put off the meeting until next Saturday,when they wouldn’t be so busy.规律精点1 所谓非限制性定语从句，顾名思义，对主句所描述的人或物起的作用，去掉后主句意思仍然完整；它与句子之间常用逗号隔开，其引导词有who,whom,whose,which,when,where,as。
that和why 不能引导分限制性定语从句。
有时用不定代词、数词或形容词最高级+of+whom/which指代先行词或先行词的一部分。
语境呈现2观察下列句子，注意划线部分的用法。
1)As is known to us,the sky is blue.The sky is blue,which is known to us.2)The big tree was cut down yesterday,as is reported in today’s newspaper.The big tree was cut down yesterday,which is about three hundred years old.规律精点2 关系代词as引导非限制性定语从句，其与which的区别在于：1)as引导的非限制性定语从句可置于句首、居中或句尾；which引导的非限制性定语从句只能置于。
（如果定语从句为否定句或表示否定意义，则使用which）。
2)as指代的是，which除了可指代整个主句内容外还可指代主句的某个部分。
1.The result of the experiment was very good, we hadn’t expected.A.whenB.whatC.thatD.which2.Lily was always talking about her wealthy huand, of course,made the other ladies unhappy.A.whoB.whichC.whatD.that3)The writer has written a number of books, only one is widely read.A.whichB.of whichC.thatD.what4)This is Mr Day, I think has something interesting to tell you.A.whoB.whomC.thatD.which5) is reported in today’s paper,people have found the lost boy.A.ItB.ThatC.AsD.What6)The result was not the same they had expected, was rather disappointing.A.which;asB.as;whichC.as;thatD.that;which高考链接1)After the flooding,people were suffering in that area, urgently needed clean water,medicine and shelter to survive.A.whichB.whoC.whereD.what2)When deeply absorbed in work, he often was,he would forget all about eating or sleeping.A.thatB.whichC.whereD.when浅谈非限制性定语从句定语从句（限制性和非限制性定语从句的区别）1.定语从句有时跟先行词的关系并不十分密切，只是作一些补充说明，不起限制作用，这种从句称为非限制性定语从句。
它常常用逗号与主句分开；翻译时常译成并列的分句。
例如：This note was left by John,who was here a moment ago.这条子是约翰留下的，他刚才来过这儿。
2.非限制性定语从句在修饰人时用who(主格),whom(宾格),whose(所有格),即：在定语从句中关系代词指人做主语时，只能用who;作宾语时，只能用whom，不能有几种选择，也不能省略，只有一种答案。
在修饰物时用which而不能用that。
总之，非限制性定语从句里没有that，也没有why。
1)Mr.Zhang,who came to see me yesterday,is an old friend of my father’s.张先生昨天来看我，他是我父亲的一位老朋友。
2)She had seven children,three of whom lived to grow up.她生了七个孩子，其中三个长大成人。
3)The team is headed by a Chinese,whose wife is a Japanese.这个对的队长是个中国人，他的妻子是日本人。
4)We visited the Jade Buddha Temple,which is in the northwestern part of Shanghai.我们参观了玉佛寺，它在上海的西北部。
5.It now has 20,000 hectares of land,more than two-thirds of which are ploughed.它有两万公顷的土地，其中三分之二以上已经耕种。
6)We walked down the village street,where they were having market day.我们沿着村庄的街道走，他们的赶集日在哪儿进行。
7)In the old days, I was a little boy,the city had no industry to speak of.过去这城市无工业可言，那时我还是个小孩。
3.引导非限制性定语从句，若关系代词所指代的先行项是整个主句，则关系代词用as或which.它们有三点相同和四点不同之处。
相同点：1)which和as都可在SVC（主语+系动词+表语）或SV（主语+谓语）结构的非限制性定语从句中作主语，此时两者可互换使用。
He said he had lost the book,which/as was true.All the schools will reopen on Sept.1(st),which/as is announced in today’s paper.2)在SVC结构的非限制性定语从句中，which和as作表语时可互换使用。
注意此时的which 或as指代上文中的表语部分。
He seemed a foreigner,which /as in fact he was.3)在SVO（主谓宾）结构的非限制性定语从句中，which和as作宾语时可互换。
I was very useful to him,which/as he realized.不同点：1) 在SVOCo(主谓宾宾补)结构的非限制性定语从句中，做主语或宾语时通常用which，而不用as.It was raining hard,which kept us indoors.2) 在SVO结构的非限制性定语从句中，做主语时通常用which，而不用as.Tom has made great progress,which delighted us.3) as引导非限制性定语从句时，通常用在表示肯定意义的从句中，而不能用在表示否定意义的从句中；which则不受此限制。
例如：She has been married again,which was unexpected.（which常在定语从句中作delay耽搁，推迟、worry、upset、make的主语，且定语从句中常含复合结构）4) as所引导的非限制性定语从句位置比较灵活，它可以位于句末，也可位于句首或居中；而which所引导的非限制性定语从句位置比较固定，通常位于句末，而不可移置句首。
例如：We can’t do without rules,as/which you know. As you know,we can’t do without rules.He failed the exam,which/as was natural. As was natural,he failed the exam.All the schools will reopen on Sept.1(st),which/as is announced in today’s paper.As is announced in today’s paper,all the schools will reopen on Sept.1(st).He admires Mr.Brown very much,which surprises me.He arrived half an hour late,which annoyed us all.My sister is a good nurse,which I am not.His sister has become a doctor,which he wants her to be.区别项目限制性定语从句非限制性定语从句形式与主句之间不用逗号隔开，口语中不停顿。
