usefulness解释为：有用, 有用性
usefulness详细解释
n.有用, 有用性
例句与用法：
Consider the postage stamp: its usefulness consist in the ability to stick to one thing till it get there.
想想那邮票吧：其用处在于它能粘住一样东西直至达到目的为止。
A regulation that has outlived its usefulness.
已经没用却仍然存在的规则
When he retired he felt that he had outlived his usefulness.
他退休后觉得自己年老无用了。
Impairment of the usefulness or value of person or property; harm.
损害，破坏对有用或有价值的人或财产的破坏; 伤害
词形变化：
副词: usefully |名词: usefulness |
详细释义：
n.
有用, 有益, 有效
He has outlived his usefulness.
他已老而无用了。
