flag captain vs captain

flag captain and captain both are nouns.

Word	Noun	Adjective	Verb	Adverb
flag captain	Yes	No	No	No
captain	Yes	No	Yes	No

As nouns, captain is a hypernym of flag captain; that is, captain is a word with a broader meaning than flag captain:

Other hypernyms of flag captain include skipper.

flag captain (noun)	captain (noun)
the captain of a flagship	a dining-room attendant who is in charge of the waiters and the seating of customers
	the pilot in charge of an airship
	the naval officer in command of a military ship
	an officer who is licensed to command a merchant ship
	a policeman in charge of a precinct
	an officer holding a rank below a major but above a lieutenant
	the leader of a group of people

flag captain (verb)	captain (verb)
	be the captain of a sports team