have and eye on，have an eye to，have an eye for
這三個短語的涵義各不相同，不能互換使用。
Have an eye on是照顧、留意、監視，它與keep an eye on同義，可互換使用。例：
Please have（keep）and eye on my child while I am away．
我不在的時候，請看管一下我的孩子。
You must have（keep）an eye on that loan shark．
你必須監視那個大耳窿的活動。
have an eye to是有欲得的願望。例：
All these countries have an eye to this island as it is rich in oil．
所有這些國家都想奪取這個島嶼，因爲它盛產石油。
Since he joined the company，he has had an eye to its financial interests and assets．
自從加入了該公司，他就覬覦公司的'財務權益及資產。
Have an eye for的意思是對有眼力、有識別的能力。例：
This old man has an eye for curios．
這個老大爺有辨別古董的眼力。
All the police dogs trained have an eye for drugs．
