同位语从句和定语从句中that的区别? that在句子中所做的成分答:引导词that在同位语从句中是连词,只起连接作用,无具体词义,that不可省略;同位语从句的名词通常有new,idea,fact,promise,question,doubt,thought,hope,message,suggestion,word(消息),possibility等.如:I’ve come from Mr wang with a message that he won’t be able to see you this afternoon....