定语从句是高中英语学习的主要语法项目之一。在高考各个题型中都有可能会涉及。它的结构和用法比较复杂，是高中阶段英语学习的一个难点，也是历年高考的热点。笔者根据多年的语法教学实践归纳出以下简易口诀，希冀对考生学习掌握定语从句的用法有所帮助。
在复合句中相当于一个“形容词”，起“定语”的作用，修饰说明名词、代词或主句全部内容的从句。
★复合句=主句 定语从句
先行词 关系词
★限制性定语从句(修饰限制、无逗号)；非限制性定语从句(附加说明、常有逗号隔开)
①关系代词(指物which，指人who，whom。既指物又指人that／whose／as)
②关系副词(指时间when，地点where，原因why)
①连接作用②替代作用③成分作用
四个核心考点： ①which／that／as
★常见句型：such／so／as／the same as…；as is known to all；as anybody can see；as is often the case；as is mentioned above；as
is reported in the newspaper；as we had expected等
②who／whom／whose
★whose n．=the n. of which／whom或of which／whom the n.
③when／where/why／the way(in which／that)
★注意一些抽象化的先行词：situation／point／case／condition／stage，activity，job／game／race／… where…；
occasion／interval，age，… when…
④介词 关系代词which /whom=whose n．
★介词选择“三原则”：从先行词的习惯搭配，从句中动词、形容词的习惯搭配，综合考虑。
★All／both，none／neither／some／any／most／half／each／many／… of which／whom…
关系词可以在从句中充当主语、宾语、定语、表语或状语。
六种特殊情况：①当先行词是不定代词au，few，little，none，nothing，anything，everything，much等，定语从句的关系代词要用that：
②当先行词被all，any，little，few，no，the only，the very，the last等修饰，定语从句的关系代词要用that：
③当先行词是最高级、序数词或被它们修饰，定语从句的关系代词要用that；
④当先行词既有人又有物，定语从句的关系代词要用that：
⑤当引导非限制性定语从句．指物或指代前面整个句子的内容，定语从句的关系代词要用which：
⑥放在介词后面指物时，定语从句的关系代词要用which。
七个易混点：①定语从句vs强调句型
It was Nov．11，2011when they got married．(定语从句)
It was on Nov．11，2011that they got married．(强调句型)
②定语从句vs名词性从句
The fact that he told us is very surprising．(定语从句)
The fact that he had not said anything surprised everybody (同位语从句)
③定语从句vs并列句
Jim passed the driving test，which surprised everybody in the office．(定语从句)
Jim passed the driving test，and it /this/that surprised everybody in the office．(并列句)
I invited Joe and Linda to dinner, but neither of them came．(并列句)
I invited Joe and Linda to dinner，neither of whom came．(定语从句)
They will fly to Kunming，where they will stay for two or three days．(定语从句)
They will fly to Kunming，and there they will stay for two or three days．(并列句)
④定语从句vs状语从句
She is such a good teacher as we all respect．(定语从句)
She is such a good teacher that we all respect her (状语从句)
⑤关系代词as／which指代整个主句时的用法区别
As is well—known to us all，smoking is harmful to our health．
It rained hard yesterday，which prevented me from going to the park．
⑥One of…，the(only)one of．．．作先行词时从句主谓一致问题
He is one of the boys who have passed the exam．
He is the only one of the boys who has passed the exam．
⑦the reason／the way等作先行词时从句引导词的选择问题
The way (that／which) he explained to us was quite simple．(作宾语)
The way (that/ in which) he explained the sentence to us was quite simple．(作状语)
一看(先行词)，二析(从句成分)，三思(特殊情况)，四选(关系词)
★速判关系代词或关系副词的关键是把先行词放到从句中，看它在从句中所作的成分。
总口诀：
在从句中“圈谓语，找主宾；缺主宾，选关系代词；不缺主宾，选关系副词。”
