carriage vs passenger car

carriage and passenger car both are nouns.

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

As nouns, carriage and passenger car are synonyms defined as:

Other synonyms of carriage include coach.

carriage (noun)	passenger car (noun)
a vehicle with wheels drawn by one or more horses	a railcar where passengers ride
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