deckhand vs Jack-tar

deckhand and Jack-tar both are nouns.

Word	Noun	Adjective	Verb	Adverb
deckhand	Yes	No	No	No
Jack-tar	Yes	No	No	No

As nouns, Jack-tar is a hypernym of deckhand; that is, Jack-tar is a word with a broader meaning than deckhand:

Other hypernyms of deckhand include gob, Jack, mariner, old salt, sea dog, seafarer, seaman, tar.

deckhand (noun)	Jack-tar (noun)
a member of a ship's crew who performs manual labor	a man who serves as a sailor