Railroad crossing train derailment - GIF

[hemmjo]

There is an easy test to check if a derailment has taken place. You look at all of the wheels. If any of the wheels are not on the rails, those wheels have derailed.

It is like being on an airplane. If you were on the plane, and then you are not on it any more, you deplaned at some point. If you were on a train, then you got off, you detrained.

Same thing with wheels and rails. The wheels used to be on the rails, now they are not.