1. (词的)使用
    Usage is the way in which words are actually used in particular contexts, especially with regard to their meanings.

    e.g. The word 'undertaker' had long been in common usage...
           undertaker一词早已广泛使用。
    e.g. He was a stickler for the correct usage of English.
           他非常注重英语的正确使用。

2. 用法；惯用法
    A usage is a meaning that a word has or a way in which it can be used.

    e.g. It's very definitely a usage which has come over to Britain from America.
           这个用法肯定是由美国传到英国来的。

3. 使用；处理；对待
    Usage is the degree to which something is used or the way in which it is used.

    e.g. Parts of the motor wore out because of constant usage...
           发动机的一些部件因为经常使用而磨损了。
    e.g. If your water usage is very small it may be worthwhile opting for a meter.
           要是用水量很小，就可以考虑装一个水表。