freight car vs gondola

freight car and gondola both are nouns.

Word	Noun	Adjective	Verb	Adverb
freight car	Yes	No	No	No
gondola	Yes	No	No	No

As nouns, gondola is a hyponym of freight car; that is, gondola is a word with a more specific, narrower meaning than freight car:

Other hyponyms of freight car include boxcar, cattle car, coal car, flat, flatbed, flatcar, gondola car, refrigerator car, tank, tank car.

freight car (noun)	gondola (noun)
a railway car that carries freight	long narrow flat-bottomed boat propelled by sculling; traditionally used on canals of Venice
	a low flat-bottomed freight car with fixed sides but no roof
	the compartment that is suspended from an airship and that carries personnel and the cargo and the power plant