railway car vs railroad car

railway car and railroad car both are nouns.

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

As nouns, railway car and railroad car are synonyms defined as:

railway car and railroad car: a wheeled vehicle adapted to the rails of railroad

Other synonyms of railway car include car, railcar.

railway car (noun)	railroad car (noun)
a wheeled vehicle adapted to the rails of railroad	a wheeled vehicle adapted to the rails of railroad