注意，对于那些由动词与介词构成的短语动词，通常不宜将它们拆开使用，此时应注意介词的位置应。如：
The boy (whom) my sister is looking after is getting better.
不能说成：The boy after whom my sister is looking is getting better. 2. 根据与定语从句中形容词的搭配来确定介词。如：
Physics is the subject in our school in which every student is interested. 物理是我们学校每个学生都很感兴趣的课程。(注意搭配 be interested in)
He referred me to some reference books with which I am not very familiar. 他我要去参考一些我不熟悉的参考书。(注意搭配 be familiar with)
3. 根据与先行词的搭配来确定介词。如：
This is our classroom, in the front of which there is a teacher’s desk. 这是我们的教室，前面有老师的讲台。(注意搭配 in the front of our classroom)
I’ll never forget the day on which she said goodbye to me. 我永远不会忘记她与我们告别的那一天。(注意搭配 on the day)
4. 根据句意来确定介词的使用。如：
This is the book from which I got the story. 这就是那本书，从中我读到这个故事。(由于句意含有“从??”的意思，所以用介词 from)
This I did at nine o’clock, after which I sat reading the paper. 九点钟时我做这事，之后我坐着看报。(由于句意含有“在??之后”的意思，所以用介词 after)
关系代词where与from where有何区别
where用作关系副词引导定语从句时，由于它本身在意义上相当于“介词+which”，所以其前通常无需再用介词。如：
This is the hotel where (=in / at which) they were staying. 这就是他们当时住的旅店。 She has a safe in her closet where (=in which) she keeps her jewelry. 她在壁橱内装有一个保险箱存放她的珠宝。
但有时我们也可见到from where的用法，这时因为from是一个比较特殊的介词，因为它有时可以后接介词短语作宾语。如：
Come out from under the table. 从桌子下边出来。
所以，尽管关系副词where在意义上相当于“介词+which”，有时由于语义的需要，也可在where之前使用介词from。如：
We went up to the roof, from where we had a good view of the procession. 我们爬上屋顶，从那儿可以很好地观看游行。
关系代词as用法说明
一、引导限制性定语从句
用在 such, same, as 等之后，引导限制性定语从句。如： I live in the same place as Tom does. 我和汤姆住在同处。 He’s not such a fool as he looks. 他并不像看上去的那样愚蠢。
He smokes as expensive a cigarette as he can afford. 他抽一种他买得起的最贵的烟。 二、引导非限制性定语从句
(2) 单独用作关系代词，引导非限制性定语从句，可放在主句之前、之后或中间，且主从句之间一般要用逗号隔开。如：
As was expected, he succeeded at last. 正如我们所料，他终于成功了。
I had coffee after dinner, as is my usual practice. 我饭后喝咖啡，这是我的习惯。 Freddie, as might be expected, was attending the conference. 弗雷迪在参加会议，这是可以预料到的。
三、as与which的用法区别
① 引导限制性定语从句的区别：as用作关系代词引导限制性定语从句时，它通常只用于 such, same, as 等之后，而which 用作关系代词引导限制性定语从句时，则用于除 such, same, as 之外的其他结构。
② 引导非限制性定语从句的区别：which引导非限制性定语从句时，通常只能位于主句后，而as引导的非限制性定语从句位于主句之前、之后或中间。
根据从句谓语动词的特点来看，as在定语从句中作主语时，从句谓语通常要有be或别的系动词，但which不受此限制。如：
Li Ming was late, which (=and this) made Mr. Zhang very angry. 李明迟到了，这件事使张先生非常生气。（不可用as)
根据句意的逻辑性来看，as引导的定语从句只表示一个众所周知或意料之中的事，但which不受此限制。如：
He married her, as [which] was natural. 他和她结婚了，这是很自然的。
He married her, which was unexpected. 他和她结婚了，这是出乎意料的。（不可用as） ■本文摘自《中学英语高频词详解词典》
关系代词whose用法说明
whose用作疑问代词或连接代词时，用法比较单一，均表示“谁的”，一般不会出错，这里主要说说它用作关系代词的用法。
1. whose用作关系代词时，它并不表示“谁的”，而是表示“??的??”，在具体语境需要灵活处理。如：
He is the man whose car was stolen. 他就是汽车被窃的人。
The boys whose names were called stood up. 叫到名字的男孩们站了起来。
You are the only one whose advice he might listen to. 你是惟一可能使他听从劝告的人。 2. 不要以为whose引导定语从句时，其先行词一定是指人的名词，其实也可以是指事物（包括动物）的名词。如：
It was an island whose name I have forgotten. 这是一座岛，名字我忘了。
Wolves are highly social animals whose success depends upon cooperation. 狼是高度群体化的动物，它们的成功依赖于合作。
3. 不仅可以引导限制性定语从句，也可引导非限制性定语从句。如：
My bitch, whose temper is very uncertain, often bites the judges at dog shows. 我的母狗脾气不稳定，常常在狗展上咬裁判。
4. 引导定语从句的“whose+名词”，有时可换成其他结构，注意词序的变化。比较： 破了窗户的那座房子是空的。
正：The house whose windows are broken is empty. 正：The house the windows of which are broken is empty. 正：The house of which the windows are broken is empty. 正：The house with broken windows is empty.
限制性定语从句还是非限制性定语从句
下面这道题是考查限制性定语从句还是非限制性定语从句? If a book is in English, __________ may mean slow progress for you. A. that B. which C. as D. and it
此题应选 A。容易误选 B。许多考生一看到空格前的逗号，就想当然地认为这是非限制性定语从句，从而误选了B。
考生可以想一想，假若此题选B(which)，which 用以引导一个非限制性定语从句，而其前又是一个以if 引导的条件状语从句，那么请问：此句的主句在哪里?
通过以上分析我们可以知道，既然本句前面有一个条件状语从句，那么后面一句就应该是主句。本题选that, 即为主句主语，全句意为：如果一本书是用英语写的，那么那就意味着你要读得慢些。
注意：当从句位于主句之前时，千万不要在主句前误加并列连词或误认为是某种从句。请做以下单选题。如：
1. When he was tired, ________ he had a rest.
A. and B. but C. so D. × 2. Because he got up too late, ________ he missed the train.
A. so B. but C. and D. × 3. Though he is poor, ________ he is happy.
A. and B. so C. but D. × 5. As is known to us all, ________ China was liberated in 1949. A. and B. but C. which D. × 答案：1. D 2. D 3. D 4. D 5. D
使用定语从句的几个误区（四）
1.误认为关系代词whose只用于修饰人
whose用作疑问代词时，主要用于指人；但用作关系代词时，它既可指人也可指物。如： It was an island, whose name I have forgotten. 它是一座岛，名字我忘了。
The factory, whose workers are all women, is closed during the holidays. 这家工厂工人都是妇女，在假期中工厂关门了。
2.混淆定语从句与并列句 请看下面两题：
(1) He has two children, and both of _______ are abroad.
A. them B. which C. whom D. who (2) He has two children, both of _______ are abroad.
A. them B. which C. whom D. who
第(1)题选A，第(2)题选C。由于第(1)题中用了并列连词and，从而使整个句子为并列句，and后应是一个独立的简单句，所以选A不选C；第(2)题没有并列连词and，both of whom are abroad为非限制性定语从句。另外，请比较下题(答案为A)：
He has two children, both of _______ being abroad.
A. them B. which C. whom D. who 3.误认为逗号后一定是非限制性定语从句
有的同学一看见逗号，就以为一定要选which而不选that，但问题是有时根本就不是定语从句。如：
(1) If a book is in English, _______ means slow progress for you. A. as B. which C. what D. that (2) When I say two hours, _______ includes time for eating. A. as B. which C. what D. that
以上两题均应选that，而不能选which，因为它们根本不是定语从句。之所以选that，是因为句中已有if和when引导的状语从句，逗号后为主句，that为主句主语。
使用定语从句的几个误区（三）
有的同学一看到先行词是表示时间、地点、原因的名词，就认为一定要用关系副词，其实也不一定。在此情况下，还要看关系词在定语从句中是用作什么成分，若是用作状语，则用关系副词，若不是用作状语(如用作主语、宾语等)则不能用关系副词，而用关系代词。比较：
This is the factory where I want to work. 这就是我想工作的工厂。(work为不及物动词where在从句中用作状语)
This is the factory that I want to visit. 这就是我想参观的工厂。(visit为及物动词，that用作visit的宾语)
The reason why he can’t come is that he is ill. 他没来的是因为他病了。(come为不及物动词，why在定语从句中用作状语)
The reason that he put forth is very important. 他提出的理由很重要。(put forth为及物动词，that在定语从句中用作其宾语)
使用定语从句的几个误区（二）