bosun vs Jack

bosun and Jack both are nouns.

Word	Noun	Adjective	Verb	Adverb
bosun	Yes	No	No	No
Jack	Yes	No	No	No

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

bosun: a petty officer on a merchant ship who controls the work of other seamen
Jack: a man who serves as a sailor

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

bosun (noun)	Jack (noun)
a petty officer on a merchant ship who controls the work of other seamen	a man who serves as a sailor