一、定语从句的定义：
用来修饰前面的名词或者代词的具有完整的主谓结构的句子就叫定语从句。定语从句有两个必备的基本元素。一个是先行词;一个是关系词。被定语从句所修饰的词称为先行词，定语从句必须置于先行词之后。
1. 先行词
(1)名词或代词做先行词。
例：He laughs best who laughs last.
(2)短语做先行词。
例：Many of life’s problems which were solved by asking family members, friends or
colleagues are beyond the capability of the extended family to resolve.
(3)句子做先行词。
例：The Greeks assumed that the structure of language had some connection with the processof thought, which took root in Europe long before people realized how diverse languages could
be.
I am a student, which you all know.
2. 关系词/引导词(关系代词、关系副词)
(1)定语从句里面关系代词的用法。
1) 常用的关系代词：which, that, who(m), whose, what, as, than。Whom现在用的很少。前面有介词时只能用which，不能用that。 定语从句的先行词为all, everything, something, nothing, anything或用作名词的little, much或先行词前有only, any, no时，先行词为序数词或形容词最高级所修饰时，先行词是两个不同性质的词，一个指人，一个指物时，先行词表示确切时间(time，day)、距离 (distance)、方向(direction)、倍数(times)、方式(way)时，关系代词用that。
2) 关系代词what, as, than在考试中的特殊情况。
A. Wh...