merchant marine vs shipping

merchant marine and shipping both are nouns.

Word	Noun	Adjective	Verb	Adverb
merchant marine	Yes	No	No	No
shipping	Yes	No	No	No

As nouns, merchant marine and shipping are synonyms defined as:

merchant marine and shipping: conveyance provided by the ships belonging to one country or industry

Other synonyms of merchant marine include cargo ships, merchant vessels.

merchant marine (noun)	shipping (noun)
conveyance provided by the ships belonging to one country or industry	the commercial enterprise of moving goods and materials
the crew of a merchant vessel	conveyance provided by the ships belonging to one country or industry