第2讲　名词性从句
名词性从句是在句子中起名词作用的句子，它的功能相当于名词词组，它在复合句中可作主语、宾语、表语和同位语，因此名词性从句又可分为主语从句、宾语从句、表语从句和同位语从句。
Many students don’t know what they should do①，but what Xiao Meng wants to do② is earn money.The reason is that she wants to lessen her parents’ burden③.It is said that many small companies need graduates to do part-time jobs②.Xiao Meng has applied for two jobs but she is not sure whether she will be employed①.She also wonders when she will be admitted to a college① and which city she will go①.She is anxious for the news that she is admitted to a good university④.
[规则感悟]　①位于及物动词或形容词之后的从句是宾语从句。②谓语动词之前的从句为主语从句。此外，该从句可以用it作形式主语。③位于be动词之后的从句是表语从句。④位于
抽象名词之后，解释该名词内容的从句为同位语从句。
1．名词性从句的引导词如下表所示
引导词
功能
从属
连词
that
在从句中不作任何成分，也没有词汇意义
whether，if
在从句中不作任何成分，意为“是否”
because，as if/though
在从句中不作任何成分，分别意为“因为”“好像”
连接代词
who(ever)，whom(ever)，what(ever)，whose，which(ever)
who(ever)和what(ever)在从句中作主语、宾语或表语；
whom(ever)在从句中作宾语；
which(ever)在从句中作主语、宾语；
whose在从句中作定语
连接副词
when(ever)，where，wherever，why，how(ever)
在从句中作状语
2．名词性从句的语序是陈述语序
Do you know where will the party be held？(×)
Do you know where the party will be held？(√)
3．名词性从句的时态
(1)当主句是现在时态(一般现在时，现在进行时，现在完成时)时， 从句可根据实际情况使用各种时态。
It annoys me that he broke my favourite vase.
他打碎了我最喜欢的花瓶，这令我很生气。
Do you know when and where he bought the book?
你知道他什么时候在哪里买的这本书吗？
I have heard that our teacher will come back tomorrow.
我听说我们的老师明天就回来了。
(2)当主句的谓语动词是过去时的时候，宾语从句若不是一个客观事实或真理，其谓语动词也用某种过去时态。
I asked her if she would allow me to interview her，and she readily agreed.
我问她是否允许我采访她，她欣然同意了。
My teacher said that the sun rises in the east and sets in the west.
老师说太阳从东方升起西方落下。 (客观真理)
4．what与that的用法
that是从属连词，在名词性从句中不充当任何成分，也没有任何意义。而what是连接代词，在名词性从句中充当成分，通常充当主语、宾语或表语。
I believe that I will succeed if I study hard.
我相信如果我努力学习我会成功的。
I believe what he said because he is an honest man.我相信他说的话，因为他是个诚实的人。
5．whether与if的用法
(1)用whether或if均可的情况
①引导大部分动词后的宾语从句时，两者均可使用。
②it作形式主语，且主语从句在句末时，两者均可引导主语从句。
(2)用whether而不用if的情况
①引导主语从句置于句首时；
②引导表语从句和同位语从句时；
③引导介词的宾语从句时；
④引导词与or not连用时；
⑤引导词后接to do时；
⑥有些动词如discuss，decide等后的宾语从句。
6．what，who，which与whatever，whoever，whichever 引导名词性从句的区别
(1)what引导名词性从句意为“什么”，带有疑问意味；意为“……的事情”，表示肯定的意思。who意思是“谁”，带有疑问意味；which意思是“哪一个”，带有疑问意味。
Do you know who broke the window?
你知道是谁打坏的窗子吗？
(2)whatever，whoever，whichever意思分别为“所……的一切事或东西”，“任何……的人”“……的任何一种东西”等，并且充当成分，相当于anything that，anyone who等。
She is very dear to me.We have been prepared to do whatever it takes to save her life.＝
She is very dear to me.We have been prepared to do anything that it takes to save her life.
她是我的至亲，我们已经准备好了不惜一切代价救她的命。
7．that不可省略的情况
(1)that引导主语从句且从句置于句首时；that引导表语从句时；that引导同位语从句时；当it作形式宾语，that引导的从句作真正的宾语时。
(2)当主句谓语后接两个或两个以上的宾语从句时，第一个that可省略，其他的that不可省略。
She said (that) her ambition was to enter a key university，that she would study hard to make her dream come true，and that she would live up to her parents’ expectations.
她说她的志向是考上一所重点大学，她会努力学习，实现自己的梦想，不辜负父母的期望。
8．同位语从句位于表示概念或思维的抽象名词之后，对该抽象名词起解释说明的作用
常见的抽象名词有news，idea，fact，promiseregister的名词，conclusion，theory，question，doubt，thought，hope，message，suggestion，word(消息)，possibility，decision等。
At first many people were astonished at the conclusion that the earth was not the centre of the universe.
起初很多人对地球不是宇宙中心这一结论感到惊讶。
9．why与because 引导表语从句的区别
why与because 引导表语从句时，前者强调结果，后者强调原因。
I had a cold.That was why I didn’t attend school.
我感冒了，因此我没去上学。
I didn’t attend school. That was because I had a cold.我没去上学，那是因为我感冒了。
注意：(1)句子的主语为the reason时，表语从句用that引导，表示原因，此时不用because。
The reason why she was ill was that she had eaten bad meat.
她生病的原因是她吃了变质的肉。
(2)由why引导的从句作主语时，表语从句用that引导。
Why we decided to put off the match was that the weather was too terrible.
我们决定推迟比赛的原因是天气太糟糕了。
10．as if/though引导的表语从句
as if/though引导的表语从句通常置于系动词look，seem，sound，be等后面，从句中既可以用虚拟语气，也可用陈述语气。
It sounds as if somebody is knocking at/on the door.
听起来好像有人在敲门。
She treats him as if he were a stranger.
她待他如陌生人。
11．同位语从句和定语从句的区别
同位语从句是用于解释说明所修饰名词的具体内容的，而定语从句是对作先行词的名词的限制、描绘或说明。that在同位语从句中只是连接主从句，没有任何意义，不在从句中充当句子成分；that在定语从句中是关系代词，不但连接主从句，而且指代被修饰的名词或代词(即先行词)，在从句中作主语、宾语和表语。
I had no idea that Brisbane has so many people! (that引导同位语从句，不能省略)
The idea (that) he put forward at the meeting is very reasonable.(that引导定语从句，作宾语，可以省略)
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