一、用法不同
1、why not:why not直接+do something。
2、why don't:why don’t+人称+do something。
二、句子结构不同
1、why not:why not可以独立成句。
2、why don't:why don't不可以独立成句。
三、时态不同
1、why not:why not没有时态的变化。
2、why don't:why don't结构可以有属时态的变化,例如变为过去why didn't。
why don't
Why don't we go and see it together?
咱们为什么不一起去看看呢?
Why don't you look in on me next time you're in town?
你下次进城顺便来看看我好吗?
Why don't you come over to England in the summer?
你为何不在夏天来英格兰呢?
why not
Why not ask someone else?
问问别人怎么样?
Why not go there at once?
为什么不马上去呢?
Why not buy an iPhone XR?
怎么不买iPhone XR呢?