定语从句解题“三步法”
定语从句是英语语法中三大从句（定语从句、状语从句和名词性从句）之一，是中学生语法学习的重点和难点，是高考必考的知识点之一。因此，掌握定语从句的解题方法对于把握句子的结构和服务高考有着重大的意义。本文重点探讨定语从句的解题方法，以抛砖引玉。
一、判断定语从句类型
1．区分定语从句和同位语从句
定语从句不同于状语从句和名词性从句的显著特点是；定语从句一定有先行词，即定语从句是放在名词或代词后修饰名词或代词的。而状语从句和名词性从句中的主语从句、宾语从句及表语从句都是没有的。因此，我们首先要区分定语从句和同位语从句。
This is the factory (that / which) his father once worked in.（先行词factory 是表示具体事物的名词，定语从句）
I will never forget the days (that/ which) we spent together in the countryside.(先行词the days是具体的时间,定语从句)
The news that our team has won the match is true..(that our team has won the match 表示the news的内容，that不充当成分，同位语从句)
The news that he told us is true.(that he told us 了news的来源，that在从句中充当宾语，定语从句)
2 区分性定语从句和非性定语从句
首先，性定语从句与先行词关系密切，不可分割。非性定语从句只对先行词起补充说明作用，没有它意义依然完整，非限性定语从句常与主句用逗号分开。如；
His mother, who is the mayor of the city, came to see me yesterday.（非性定语从句who is the mayor of the city 说明先行词his mother的身份，此句话不可用性定语从句。）
His brothert who is the mayor of the city came to see me yesterday. ( 定语从句who is the mayor of the city了先行词 his brother，说明书他有几个兄弟，来看我的是当的那个)
其次，that 不能用于引导非性定语从句是that 和which的区别之一。
He turned a deaf ear to our demands, which enraged all of us.
They have invited us to visit their country, which is very kind of them.
在上述的两个句子中，which都不能用that代替
最后，as用于性定语从句和非性定语从句结构和意义不同。
As用于性定语从句时，先行词前常有the same, such等，构成特殊的句式。
...the same ＋先行词＋as...（表示“与......一样”之意）
...the same ＋先行词＋that...（表示“正是” “就是”之意）
This is the same wallet as I lost yesterday. (这个钱包我和昨天丢的那个一样)
This is the same wallet that I lost yesterday. (这个钱包就是我昨天丢的那个)
as在非性定语从句中位置灵活，可在句首、句中和句末，含有“正如……”之意。而which引导非性定语从句时，只能放在先行词之后。表示“这一点，这件事”。
As is known to all, he is good at maths.
He is good at maths, as is known to all.
二、观察先词的类型和特点
1.先行词是表示时间、地点、原因的名词，在从句中作状语时分别用when, where, why ,where..在从句中作主、宾时用that /which.。
I will never forget the day when I joined the Patty.
This is the building where Luxun once lived in.
That was the reason why he didn’t come to school.
Can you find a case where this word can be used?
This is the man who helped me with my lugguage the other day.
This is the book which is worth reading twice.
2.先行词是不定代词。先行词是指事物的不定代词，如all anything，nothing，something,定语从句一般用that, 先行词是指人的不定代词，如someone，somebody,
no one,bobody,anybody,定语从句仍用who或whom引导。
All that glitters is not gold.
Anything that can be done has been done.
Anyone who wants to take the trip has to sign here.
3.观察先行词的修饰语。如先行词前有序数词或形容词最高级修饰，一般用that 引导。
This is the first English movie that I have seen.
It is the most beautiful city that I have been to.
4.观察先行词的数量。有两个先行词，一个指人一个指物时，定语从句用that 引导。
They talked for half an hour of the things and persons. (that ) they remembered at school
We have learned about the writer and the book that he reffered to in his speech.
三、分析从句结构
定语从句中最关键的一步是选择引导词，即关系代词和关系副词。在确定从句类型和先行词后，需要分析从句的结构来最后确定引导词用关系代词还是关系副词。根据关系词的选择需要，我们可把句子分为两种结构。SV结构和SVO结构。
