disappearance

n. 消失

The act or an instance of gradually diminishing in brightness, loudness, or strength until actual disappearance occurs.

逐渐消失在亮度、响度或精力上逐渐减弱直至全部消失的活动或例子

He was hard put (to it) to explain her disappearance.

他难以说明她为什麽不见了.