Engines, machines and motors. How do you define them? Are they the same thing? How many ways have we used these words interchangeably? What is correct. It’s not that straight forward as you may think. Before answering, you may want to Google a bit. I found conflicting answers. Examples of a catapult being an engin of war and a machines of torture. Ford Tri Motor airplane. What is a water wheel at an old mill? How do you define which is which?