怎么区分英语上的同位语从句和定语从句?

定语从句与同位语从句的区别.
①定语从句引导词被称为关系词,that充当主语、宾语、表语.有时可省略.
②同位语从句引导词被叫做连词,that不能充当任何成分,不可省.
Word came that their army was defeated.(同位语)
We expressed to them our wish that was the same as their.(定语)