purser vs ship's officer

purser and ship's officer both are nouns.

Word	Noun	Adjective	Verb	Adverb
purser	Yes	No	No	No
ship's officer	Yes	No	No	No

As nouns, ship's officer is a hypernym of purser; that is, ship's officer is a word with a broader meaning than purser:

purser: an officer aboard a ship who keeps accounts and attends to the passengers' welfare
ship's officer: a person authorized to serve in a position of authority on a vessel

Other hypernyms of purser include officer.

purser (noun)	ship's officer (noun)
an officer aboard a ship who keeps accounts and attends to the passengers' welfare	a person authorized to serve in a position of authority on a vessel