bobby vs officer

bobby and officer both are nouns.

Word	Noun	Adjective	Verb	Adverb
bobby	Yes	No	No	No
officer	Yes	No	Yes	No

As nouns, officer is a hypernym of bobby; that is, officer is a word with a broader meaning than bobby:

Other hypernyms of bobby include police officer.

bobby (noun)	officer (noun)
an informal term for a British policeman	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

bobby (verb)	officer (verb)
	direct or command as an officer