Check in: (在旅馆、机场、大会等处)办理登记手续,报到,登记
He has just checked in at the hotel.
他刚刚在旅馆办好住宿手续。
We checked in at the airport an hour before our plane took off.
我们在飞机起飞前一小时到达机场办理登机手续。
Check out: (从旅馆等)结账离开
They checked out ten minutes ago.
他们十分钟前就结账走了.