merchant vessels vs cargo ships

merchant vessels and cargo ships both are nouns.

Word	Noun	Adjective	Verb	Adverb
merchant vessels	Yes	No	No	No
cargo ships	Yes	No	No	No

As nouns, merchant vessels and cargo ships are synonyms defined as:

merchant vessels and cargo ships: conveyance provided by the ships belonging to one country or industry

Other synonyms of merchant vessels include merchant marine, shipping.

merchant vessels (noun)	cargo ships (noun)
conveyance provided by the ships belonging to one country or industry	conveyance provided by the ships belonging to one country or industry