is a specific kind of: car, railcar, railroad car, railway car.

is a broader term that covers: buffet car, diner, dining car, dining compartment | nonsmoker, nonsmoking car | chair car, drawing-room car, palace car, parlor car, parlour car | Pullman, Pullman car | sleeper, sleeping car, wagon-lit | smoker, smoking car, smoking carriage, smoking compartment.

is a member of: passenger train.