名词性从句分为四类：主语从句,表语从句,同位语从句及宾语从句
在英语中主语,宾语,表语,同位语都可以用名词来充当,所以一个完整的句子做这些成分称为名词性从句.
定语从句是一个句子修饰一个名词,名词称为先行词,如a girl (who is standing on the mountain )括号内就是定语从句,修饰Agirl．
而定语从句分为两类：一类是直接限定的,另一类是非限制性从句,如：agirl,who is standing on the mountain.
如下是我的一些积累,以供参考：
1.名词性从句
1.1 主语从句
陈述句做主语从句,引导词为that,多以it来做形式主语
e.g It is difficult that everyone can be as excellent as you.
一般疑问句做主语从句,引导词为whether.
e.g whether your decision is right is confusing most of us.
特殊疑问句做主语从句,引导词为特殊疑问词(when,where,how many,how much,等)
e.g What you have said is right definitely.
1.2 宾语从句
陈述句做宾语从句,引导词为that,有时以it来做形式主语,that可省略.
e.g She knows that she has been wrong.
一般疑问句做宾语从句,引导词为whether或if.
e.g She asked me whether/if my homework has been finished.
特殊疑问句做宾语从句,引导词为特殊疑问词(when,where,how many,how much,等)
e.g She has known how much money I had.
1.3 表语从句
陈述句做表语从句,引导词为that,不可省略
e.g The answer is that he has been a rich.
一般疑问句做表语从句,引导词为whether.
e.g The question is whether you have tried it or not.
特殊疑问句做表语从句,引导词为特殊疑问词 (when,where,how many,how much,等)
e.g The question is why you have been so foolish.
1.4 同位语从句
陈述句做同位语从句,引导词为that,不可省略
e.g We all know the fact that you are a liar.
一般疑问句做同位语从句,引导词为whether
e.g The question whether you are his son is unknown
特殊疑问句做同位语从句,引导词为特殊疑问词(when,where,how many,how much,等)
e.g The question when I could come back cannot be answered now.
2.形容词性从句
定语从句:限定性定语从句和非限定性定语从句
引导词有：that,which,who,whom,介词+which
构成部分：先行词+引导词+从句的其他部分(其中先行词是被修饰词)
先行词的选择：
物时：which/ that
Genetic engineering is a safe and powerful tool which/that will yield unprecedented
results,specifically in the field of medicine.
基因工程是一种安全和威力强大的工具,特别是在医学领域将产生史无前例的成
效.
人：who(主语或宾语)/whom（宾语）
Those people who are against mandatory retirement have the following reasons.
那些反对强制退休制度的人持有以下理由.
人和物：that
My dog and I that was trapped in the cave for several days was saved by a passer-by fortunately.
谁的：whose
The tall building whose windowed was broken was ruined in the war.
时间：when====介词+which
I look forward to a day when we can enjoy a delicious meal at your restaurant.
=I look forward to a day on which we can enjoy a delicious meal at your restaurant.
区分：I look forward to the day which is coming soon.
地点：where====介词+which
I prefer to live in a place where the climate is agreeable.
=I prefer to live in a place in which the climate is agreeable.
原因：why====介词+which
That is the reason why many people are strongly against the ban on pets in big cities.
That is the reason for which many people are strongly against the ban on pets in big cities.
非限制性定语从句：,which/介词+which
Language extinction is a gradual process,which tends to affect the minority tribes most keenly.
语言灭绝是一个缓慢的过程,对少数民族部落的影响最大.
As can be seen in the graph,the number of girls increased gradually in the next year.
