1.For sale的意思是“待售的”

比如我们说 That apartment is for sale. 意思是“这套公寓是等待出售的。”

2.On sale的意思是 “打折，降价出售”。

如 This car is on sale this weekend. That kind of suits are on sale this month.

请注意不要把on sale 与 for sale混淆起来。