定语从句的概述 写法
定语从句是非常重要的。鉴于它的重要，将定语从句分成四部分进行探讨。
一、定语从句的概述：
一个句子作定语，用来修饰限定名词。例如：
Law is a discipline which encourages responsible judgment.
全句为主句，discipline名词，用which encourages responsible judgment.修饰。
注意：定语从句可以修饰所有名词。被修饰的名词称为先行词，因为定语从句所修饰的名词一定放在从句前面，用关系词连接，且关系词与先行词是同等的。例如上面的句子可分解为：Law is a discipline. A discipline encourages responsible judgment.若将两句话构建成一句话，那么出现有重复的名词，在英语中我们就用一定的词来替换有重复的词。如是替换人则用who，替换物则用which。用来替换的关系词是要作句子成分的，故一定一定不能省略。
二、定语从句的写法
先行词n. + 关系词 + 陈述句（定语从句）
关系词选择看先行词是表示什么。
注意：whom是专门作宾语的。先行词是事/物，关系词选择which/thatTeachers need to be aware of the emotional,intellectual,and physical changes that young adults experience.
changes先行词（表示的是变化这件“事”）故用了that
Furthermore,the legal system and the events which occur within it are primary subjects for journalists.
events先行词（表示事件）用which修饰。
2、先行词是人，关系词选择who/whom/that
who/that只要是指人，都能通用，但是whom只能用做宾语。
Most archaeological sites,however,are discovered by archaeologists who have set out to look for them.
archaeologists（先行词表示人的）故用who作关系词。
Retailers that master the intricacies of wholesaling in Europe may well expect to rake in substantial profits thereby.
Retailers（先行词表示人物的）用that作关系词。that master the intricacies of wholesaling in Europe陈述句作从句。
3、先行词是人/物，表示人或物的所有关系（即XX的），关系词选择whose。
On display here are various fantasy elements whose reference,at some basic level,seems to be the natural world.
这个句子倒装过的，顺序排列应该是：Various fantasy elements are on display here...
之所以倒装是因为后面有定语从句修饰various fantasy elements，如果按顺序排列的话使句子看起来头重脚轻。“这些元素的参考”XX的所以用whose关系词。
This, for those as yet unaware of such a disadvantage,refers to discrimination against those whose surnames begin with a letter in the lower half of the alphabet.
4、先行词是时间，关系词选择when
It is difficult to the point of impossibility for the average reader under the age of forty to imagine a time when high-quality arts criticism could be found in most big-city newspapers.
5、先行词是地点，关系词选择where
In dreams, a window opens into a world where logic is suspended and dead people speak.
6、先行词是原因，关系词选择why
The other reason why costs are so high is the restrictive guild-like ownership structure of the business.
重点关注前两种定语从句。
关于定语从句的关系词的几点注意：1、定语从句的关系词每一个都必须作成分，包括that。
2、whom指人，只能在做宾语时使用。
3、when/where/why引导定语从句时，前面的先行词必须与之匹配。
4、关系词在定语从句中作宾语时，都可以省略。无论及物动词后（动宾）还是介词后（介宾），均可以省略。
5、关系词一定在从句句首，但是它表示的成分不一定在句首。
Are humans actually aware of the world they live in?
可以在they live in前面加上关系词which，但实际它表示的成分在live in后作宾语。
These rules say they must value some assets at the price a third party would pay,...
a third party would pay可以是which a third party would pay,但是which所表示的成分应该在pay后面作宾语。
注意：特殊的关系词whereby = by which（近15年出现过2次）
The definition also excludes the majority of teachers,despite the fact that teaching has traditionally been the method whereby many intellectuals earn their living.
可以将whereby换成by which。
今天我们就讨论在这里，下次我们探讨定语从句的分类。