概念:
1.在句子中修饰名词或代词，
定语从句在句中充当定语。
2.定语从句必须有
先行词，并尽量靠近先行词。
3.在定语从句中，关系词在从句中充当成分。
关系代词与关系副词
关系代词：
1）指人： who(主格)， whom(
宾格)，whose(
所有格)
2）指物： which(主格，宾格)， whose(所有格)
3）指人或物： that
1. This is the book which/that my mother bought yesterday. 一般情况：指物which/that都可以
2.This is the teacher who/that teaches us English. 一般情况：指人作主语who/that都可以
3.That is the man whom/who/that you are looking for. 一般情况：指人作宾语who/that/whom都可用。
以下情况指物时只能用that而不能用which:
1)先行词是all， no， none， everyone， something， much， little等。如：
All that he can do is to do nothing。
2)先行词前有序
数词/形容词最高级/the last/ the same/ the only等。 如：
Shanghai is the biggest city that lies in the east of China.
Is this the only factory that your father once worked in?
3) 先行词既有人又有物时：
He talked about the writer and his books that interests him.
4) 主句是以who/which开头的
特殊疑问句时 (避免重复}
Which is the bus that you want to take?
Who is the boy that is lying on the ground?
关系副词where/when/why的用法：where指地点 / when指时间 / why 指原因。
1) That is the day when I got married. (指时间，作时间状语，用when) 那就是我结婚的那一天.
比较：我永远不会忘记我们一起在农村度过的那一个月:
a) I’ll never forget the month when we stayed together in the country. （指时间，且we stayed together in the country句意完整）(we stayed together in the country in that month.)
b) I’ll never forget the month that/which we spent together in the country.。(从句缺少宾语，故用that/which引导，作它的的宾语)(we spent the month together in the country.)
2) That is the school where I work as a teacher. (指地点，从句I work as a teacher句意完整，故school为地点状语用where) 那就是我在那儿教书的那所学校。
3) This is the factory which/that we visited (visit及物动词，后跟物，故用which/that)
4) This is the place where we lived for five years.(live
不及物动词，后跟地点故用where)
5）The reason why he came so early is not known.（why指原因）
6）The reason why we was late is that our car did not come.
= The reason that our car did not come is why we was late
另where/when/why 可用“介词+which ”来代替:
This is the place where we lived for five years.= This is the place in which（where） we lived for five years.
I never forget the day when I joined the PLA. (注意从句句意完整)=I never forget the day on which I joined the PLA.
The reason why he diden’t attened the meeting isn’t known.=The reason for which he diden’t attened the meeting isn’t known.
关系代词在从句里做定语时，只能用whose （ Whose作定语限定人或物，有物主关系）
1) This is the boy whose father is a scientist.
2) Her parents woulden’t let her marry anyone whose family was poor.
关于定语从句，高初中语法书里都由详细讲解，反复看就会懂的哦。
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