考向一 非限制性定语从句非限制性定语从句是对意义已经非常明确的先行词给予补充、说明，删去非限制性定语从句，主句的意思仍是概念清晰、结构完整的非限制性定语从句的引导词有who，whom，which，whose，as，when，where等，that不可用于引导非限制性定语从句，从句之前要用逗号先行词指人，则用who，whose，which等；先行词指物，要用which；先行词表时间或者地点，并在句中作时间状语或者地点状语时要用when或者where引导一、使用非限制性定语从句的情况：1. 关系代词指代整个主句时，使用非限制性定语从句☛You did a lot for me, for which I was grateful. 你为我做了许多，对此我很感激☛The Diaoyu Island belongs to China, as is known to us. 众所周知，钓鱼岛属于中国☛A middle-aged woman killed her husband, which frightened me very much. 一个中年女子杀害了自己的丈夫,这令我十分恐惧2. 当先行词指的是世界上独一无二的事物或人名地名等专有名词时，使用非限制性定语从句。
☛China, which is my motherland, is developing fast. 中国是我的祖国，正在快速发展☛Eason, who was a pop star, got married last year. 伊森去年结婚了，他是明星☛Last Sunday they reached Nanjing , where a conference was to be held. 他们上周日到达南京，有个会议要在那里举行3. 当先行词指的是某人只有一个亲属（son，daughter等）时，使用非限制性定语从句☛He has a daughter, who is studying in London. 他有个女儿，现在正在伦敦学习只有一个女儿）☛This is my teacher, who has something to tell you. 这是我的老师，他有一些事情要告诉你 二、限制性定语从句与非限制性定语从句的区别1. 形式不同 限制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；而非限制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 2. 功能不同 限制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；而非限制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。
☛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掉，句子意义仍然完整) 3. 翻译不同 在翻译定语从句时，一般把限制性定语从句翻译在它所修饰的先行词之前，而把非限制性定语从句与主句分开☛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 4. 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) 5. 先行词不同 限制性定语从句的先行词只能是名词或代词，而非限制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。
☛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) ☛Her father, who has a lot of money, wishes her to study abroad. 她父亲很有钱，希望她出国学习先行词为表独一无二意义的普通名词，要用非限制性定语从句修饰) 6. 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，而在非限制性定语从句中关系词一律不能省略 考向二 as，which引导的定语从句一、相同点两者引导非限制性定语从句时，可指代主句中的部分或整个句子的内容，在从句中作主语、宾语或表语，位于主句之后有时可互换。
☛The meeting was put off, as /which was exactly what we wanted. 会议被推迟了，这正是我们想要的☛He was a doctor, as/which I knew from his manner. 他是一名医生，我是从他的举止中知道的二、不同点1. as可以放在主句前后，也可插入主句之中；而which引导的非限制性定语从句只能位于主句之后☛As is known to all, fish can’t live without water. 众所周知，鱼离开水无法生存☛Air, as we know, is gas. 正如我们所知，空气是气体2. 在非限制性定语从句中，which后的be动词不可省；而as后的be动词可以省略☛She told me she won the match, which was a lie. 她告诉我们她赢得了比赛，这是一个谎言☛The material is elastic, as (was) shown in the figure. 这种材料是有弹性的，正如图中所示3. which在非限制性定语从句中作主语时可用各类动词作谓语；而as作主语时，谓语常用系动词，如be，seem，become等，一般不用其他行为动词。
☛He saw the girl, which delighted him. 他看见了那个女孩，这让他很高兴☛He didn’t say anything at the meeting, as/which seemed very strange. 他在会议上一言未发，这看起来非常奇怪4. as常用＂正如＂含义，常用的结构有as we know（众所周知）；as often happens（正如常发生的那样）；as is often the case（情况常常如此）；as we all can see（正如我们看到的）；be announced / expected / known / imagined / mentioned / said / shown / reported等这些结构常放句首，偶尔也可以放句中或句末☛As is known to all, China is a developing country. 众所周知，中国是一个发展中国家☛Kate was late for school, as often happened. 凯特上学迟到了，正如常发生的那样5. 在非限制性定语从句中，which可指代主句中的某一个单词，as不可以。
☛My brother enjoyed playing basketball, which he really plays well. 我哥哥喜欢打篮球，他打得非常好☛Beijing, which he was born in, is our capital. 北京，他出生的地方，是我们的首都6. ＂介词+关系代词（介宾代物）＂中关系代词只能用whichThe Travel Agency, with which our company has been dealing for several years, has opened for new branches. 那家与我们交易了好几年的旅行社又开了新的分店☛Air is a mixture of gases, of which oxygen forms 21 percent. 空气是一种气体的综合体，其中氧气占了21%7. 从句中的谓语动词是否定形式时，常用which☛He can write a letter in English, which I can not. 他可以用英语写信，我不能☛Metal will bear beating with a hammer, which a stone will not. 金属能承受得住用锤子敲打，但是石头则不能。
8. 非限制性定语从句中的关系代词代表前面主句中的宾语从句时，常用which☛He said he had passed the exam, which was untrue. 他说他通过了考试，这是假的。
