coach vs railroad car

coach and railroad car both are nouns.

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

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

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

coach (noun)	railroad car (noun)
a carriage pulled by four horses with one driver	a wheeled vehicle adapted to the rails of railroad
a railcar where passengers ride
a vehicle carrying many passengers; used for public transport
a person who gives private instruction (as in singing, acting, etc.)
(sports) someone in charge of training an athlete or a team

coach (verb)	railroad car (verb)
teach and supervise (someone); act as a trainer or coach (to), as in sports
drive or operate a coach or carriage