同位語(yǔ),顧名思意,就是從句與先行詞是在句子中是一樣的成分.也就是說(shuō),去掉同位語(yǔ)從句句子在語(yǔ)法上還是成立的.
而表語(yǔ)從句不同.表語(yǔ)是一句句子,去掉了表語(yǔ)從句句子語(yǔ)法上語(yǔ)意上都會(huì)出現(xiàn)問(wèn)題.
你舉得例子的問(wèn)題在于：The news came that we had won the first prize中that we had won the first prize確實(shí)是news的同位語(yǔ).但是這不是一句句子.這只是先行詞+同位語(yǔ)從句而已
而The news was that we had won the first prize這是一句完整的句子了已經(jīng).
The news that the puma has been at large now is widely spreaded
這句話中才是一個(gè)完整的句子.主干是The news now is widely spreaded
that the puma has been at large是同位語(yǔ)從句,補(bǔ)充說(shuō)明news的內(nèi)容.去掉的話句子還是成立的