effective是有效的，起作用的意思，用于事物或人，一般是呈现出正确的结果或是解决了问题。例句：

The government took effective measures to reduce the price.***采取了有效措施来降低物价。

efficiency

n.效率；效能；功效

The workers in this factory are working without morale and the efficiency is of course low.这家工厂的工人干起活来毫无士气，效率当然也很低。