1. 概念：就是把一个完整的句子当一个名词来使用。那么从句就具备了名词所具备的所有性质。主语、宾语、表语、同位语。
　　2. 引导名词从句常用的连词。有三类：1）that; 2)whether,if; 3)when,where ,how等连接副词或what,who,whose等连接代词。
　　That引导的名词性从句不能做任何句子成分。what一定在从句中充当主语或者宾语。Which 和whose 后面必须接名词。例如：
　　Concerns were raised __witness might be encouraged to exaggerate their stories in court to ensure guilty verdicts.
　　A.what     B.when   C.which    D.that
　　3)多重的名词从句现象。例如：
　　I realized that what I said was not exactly what meant to say.
　　考题：Prof. Lee’s book will show you ________ can be used in other contexts.
　　[A] that you have observed
　　[B] that how you have observed
　　[C] how that you have observed
　　[D] how what you have observed

　　
　　二、名词从句中的主语从句

　　主语从句有如下几种表示方式：
　　1.用which, that放在句首引导主语从句。例如：
　　That the seas are being overfished has been known for years.
　　3.用it is +ved+that…例如：
　　It is believed that you are good boy.
　　3. 用whether引导主语从句。例如：
　　Whether the eyes are the windows of the soul is debatable.

　　三、宾语从句

　　需要掌握的几点：
　　及物动词后面的宾语从句。2005年例句：
　　Do you remember all those years when scientists argued that smoking would kill us?

　　四、表语从句

　　就是一句话做另一个句子的表语。就是把从句放在系动词的后面。1997年例句：
　　A report consistently brought back by visits to the US is how friendly, cautious and hopeful most Americans were to them.

　　五、同位语从句

　　就是用来补充说明同位语的名词成分的句子。结构是：名词+that+从句。
　　同位语从句与宾语从句和定语从句的区别：引导宾语从句和定语从句的的that, which可以省略，而引导同位语从句的that不能省略。定语从句中的that必须在从句中扮演主语或者宾语。同位语从句的that不扮演任何成分。例如：
　　There is a popular saying that family instability causes social instability.  that不做句子成分。