If something is missing or has gone missing, it is not in its usual place, and you cannot find it.
It was only an hour or so later that I discovered that my gun was missing.
也就是大约一个小时后,我发现自己的枪不见了。
If a part of something is missing, it has been removed or has come off, and has not been replaced.
Three buttons were missing from his shirt.
他的衬衫少了3颗纽扣。
If you say that something is missing, you mean that it has not been included, and you think that it should have been.
She had given me an incomplete list. One name was missing from it.
她给了我一份不完整的名单,有一个名字漏掉了。
Someone who is missing cannot be found, and it is not known whether they are alive or dead.
Five people died in the explosion and more than one thousand were injured. One person is still missing.
爆炸中5人丧生,一千多人受伤,还有1人失踪。
missing in action
If a member of the armed forces is missing in action, they have not returned from a battle, their body has not been found, and they are not thought to have been captured.