Power train and Piston

Power train noun - Wheelwork consisting of a connected set of rotating gears by which force is transmitted or motion or torque is changed.

Piston and power train are semantically related in engine topic. In some cases you can use "Piston" instead a noun phrase "Power train", when it comes to topics like device that drives a machine.

Piston noun - Mechanical device that has a plunging or thrusting motion.

Power train and piston are semantically related in engine topic. You can use "Power train" instead a noun "Piston", if it concerns topics such as device that drives a machine.