that在定语从句和同位语从句中的区别

相信对于很多学生来说that在定语从句和同位语从句中的区别是非常困难的。那么究竟有什么区别呢下面就让我们一起来看看吧！
1: that在定语从句中充当关系代词代替前面的先行词在从句中做主语或者宾语。例如The cat that mother bought yesterday was lovely. that作为bought的宾语。
that在同位语从句中只是一个引导词 连接词不作为句子的成分。例如The thing that Tom was ill was true. that在从句中不做任何句子成分。
2: that在定语从句中对先行词起到修饰和限制的作用。例如The bird that on the tree is beautiful. that修饰限定先行词bird。
that在同位语从句中起到对前面名词的解释或者补充说明作用。例如The idea that we should help her is great. that对idea进行解释说明。
3: that在定语从句中引导的先行词通常为名词或者代表。例如The box he bought was yellow. box为名词。
that在同位语从句中引导的先行词通常为抽象名词。例如The news that he was dead was known by them. 其中先行词news为抽象名词。
4: that在定语从句中可以省略。例如The dog that in the box is little. 句中that可以省略。
that在同位语从句中不能省略。例如The news that Tim was lost was true. 句中that不能省略。