1.同位于从句与前面名词是同位关系,即说明前面名词的内容
定语从句与前面名词是修饰与被修饰关系,即限定名词的范围
e.g The news that I have passed the exam is
true.
The news that he told me just now is
true.
2.同位于中的that是连词,但a.不充当任何成分；b.没任何意义；
c.不能省略
定语从句中的that是关系代词,除连接作用外,还可充当主、宾
等（作宾语时可省略）
e.g.The idea that computers can recognize
human voices surprises many people.
The idea that he gave surprises many
people
如何判断一从句是定语从句还是同位于从句?
用系动词be的形式去判断,如果是"表语从句"则是同位语从句,否则为定语从句.