disappearances
If you refer to someone's disappearance, you are referring to the fact that nobody knows where they have gone.
appearance , reappearance
Her disappearance has baffled police.
她的失踪令警方大为困惑。
If you refer to the disappearance of an object, you are referring to the fact that it has been lost or stolen.
Police are investigating the disappearance of key files on the killers.
警方正在调查有关杀人凶手的关键性档案丢失的事件。
The disappearance of a type of thing, person, or animal is a process in which it becomes less common and finally no longer exists.
the virtual disappearance of common dolphins from the western Mediterranean in recent years.
普通海豚近年来在地中海西部真正的绝迹。