ship's officer vs officer

ship's officer and officer both are nouns.

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

As nouns, ship's officer and officer are synonyms defined as:

ship's officer and officer: a person authorized to serve in a position of authority on a vessel

ship's officer (noun)	officer (noun)
a person authorized to serve in a position of authority on a vessel	a member of a police force
	someone who is appointed or elected to an office and who holds a position of trust
	any person in the armed services who holds a position of authority or command
	a person authorized to serve in a position of authority on a vessel

ship's officer (verb)	officer (verb)
	direct or command as an officer