carriage vs railroad car

carriage and railroad car both are nouns.

Word	Noun	Adjective	Verb	Adverb
carriage	Yes	No	No	No
railroad car	Yes	No	No	No

As nouns, railroad car is a hypernym of carriage; that is, railroad car is a word with a broader meaning than carriage:

Other hypernyms of carriage include car, railcar, railway car.

carriage (noun)	railroad car (noun)
a vehicle with wheels drawn by one or more horses	a wheeled vehicle adapted to the rails of railroad
a railcar where passengers ride
a machine part that carries something else
a small vehicle with four wheels in which a baby or child is pushed around
characteristic way of bearing one's body