1.同位语从句中that引导的从句就是that前面那个名词的内容.
试比较:The news that the leader will come here is not true.(同位)
The news that you told me last week is not true.(定从)
而且that在同位语从句中不充当成分
而定从中,that指代news充当从句宾语.
2.在that 前面加is,如果句意成立就是同位语;否则就不是,
The news is that the leader will come here is not true.(成立)
The news is that you told me last week is not true.(不成立)
以上两种方法可以帮助判断