1.表语从句是放在系动词后面的从句,也就是在be,seem,look,appear后面.
It looks as if it is going to rain.
2.同位语从句是放在名词后面,对前面的名词进一步说明的,常跟同位语从句的名词有newsnews,idea,fact,promise,question,doubt,thought,hope,message,suggestion,word（消息）,possibility等.
I’ve come from Mr wang with a message that he won’t be able to see you this afternoon． 我从王先生那里来,他让我告诉你他今天下午不能来看你了.
The news that our team has won is true.
祝学习愉快!