officer vs investigator

officer and investigator both are nouns.

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

As nouns, investigator is a hyponym of officer; that is, investigator is a word with a more specific, narrower meaning than officer:

officer (noun)	investigator (noun)
a member of a police force	someone who investigates
someone who is appointed or elected to an office and who holds a position of trust	a scientist who devotes himself to doing research
any person in the armed services who holds a position of authority or command	a police officer who investigates crimes
a person authorized to serve in a position of authority on a vessel

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