car carrier vs cargo ship

car carrier and cargo ship both are nouns.

Word	Noun	Adjective	Verb	Adverb
car carrier	Yes	No	No	No
cargo ship	Yes	No	No	No

As nouns, cargo ship is a hypernym of car carrier; that is, cargo ship is a word with a broader meaning than car carrier:

car carrier: a cargo ship specially fitted for the transport of large quantities of cars.
cargo ship: a ship designed to carry cargo

Other hypernyms of car carrier include cargo vessel.

car carrier (noun)	cargo ship (noun)
a trailer that can be loaded with new cars for delivery to sales agencies	a ship designed to carry cargo
a cargo ship specially fitted for the transport of large quantities of cars.