10、关系代词as,在从句中作主语、宾语和表语。
(1)先行词被such和the same修饰，或句型as many(much)中，从句都用as 引导。
Such books as you bought are useful. The school is just the same as it was 10 years age.
注意：区别①such … that … 引导的结果状语从句。They are such lovely children that we love them much .②the same … that … 引导定语从句。I want to use the same tool that you used just now.
(2)无先行词的定语从句用as和which引导。
区别：①意义上：as 含有“这点正如……一样”。②位置上：as 从句可置句首，也可在另处。
He didn’t pass the exam, as we had expected.
There is lots of air in loose snow, which can keep the cold out.
As is known, the earth is round, not flat.
9、whose作关系词既指人又指物，在从句中作定语。如：
Do you know Mr. Smith whose story is very moving?
There is a room, whose window faces the river.
There is a room, the window of which faces the river.
8、关系词who与that指人时，也有不同情况分别用不同的关系词
(1)当主句是there be句型时，关系词用who。
(2)先行词是为anyone、those、someone、everyone、one等词时，关系词用who。
(3)当主句是who作疑问词时，关系词用that。
Who is that girl that is standing by the window?
(4)whom在从句中只作宾语，可被who取代。
7、宜用which而不用that的情况
(1)在非限制性定语从句中
(2)在关系词前有介词时
(3)当先行词本身是that时
(4)当关系词离先行词较远时
6、在定语从句中，当先行词指物时，下列情况的关系词宜用that而不用which
(1)先行词被①形容词最高级 ②序数词 ③数词几种词修饰或被 ④only、any、few、little、no、all、one of等修饰时。
(2)先行词为all、much、little、none、few、one、something、anything等不定代词时。
(3)先行词中既有人又有物时。
He was looking pleasantly at te children and parcels that filled his bus.
(4)先行词在主句中作表语关系词在从句中作表语时。
The village is no longer the one that was 5 years ago.
(5)当主句中含有疑问词which时。
Which are the books that you bought for me ?
5、确定关系词的步骤
(1)先找关系词，看先行词指的是什么。
(2)看关系词在从句中所充当的成分。
4、关系词：引导定语从句的都称关系词
关系代词：who, whom, which, that, whose, as。
关系副词：when, where, why。that偶尔也作关系副词。
3、先行词：被定语从句修饰的词称为先行词
(1)先行词一般是名词和不定代词，如:some-, any-, every-和no与-boy, -thing的合成词；或all、none、any、some、that、those等代词。数词也可以作先行词，人称代词也同样可作先行词。
(2)先行词与关系词是等量关系。必须注意两点：
①先行词在从句中作主语时，从句谓语动词的数由先行词而定。
This is the place which is worth visiting.
②关系词在从句句子中充当了成分，其意思就是先行词的意义，所以在从句中不能重复其意。
There are many places we can visit(them)in China.
2、位置：定语从句置于被修饰词之后
Those who are willing to attend the party, sign here please.
1、功能：相当于形容词，修饰名词或代词，在句中作定语