Check – phrasal verb

Check in – to tell the official that you’ve arrived (at hotel, airport and such)

The passengers must check in 2 hours before the scheduled departure of the flight.

Check out – pay the bill in the hotel and leave

The guests are required to check out by 10am.

Check out – to be found to be true after examination

The police found that her story didn’t check out.

Check over – to examine something carefully

Check over you essay for mistakes before you hand it in.

Check up on – to find out that something is true or correct

The police checked up on my version of events.

Check up on somebody – make sure that the person is doing what he/she should

He’s gone to check up on his subordinates.