researcher vs investigator

researcher and investigator both are nouns.

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

As nouns, researcher and investigator are synonyms defined as:

researcher and investigator: a scientist who devotes himself to doing research

Other synonyms of researcher include research worker.

researcher (noun)	investigator (noun)
a scientist who devotes himself to doing research	someone who investigates
	a scientist who devotes himself to doing research
	a police officer who investigates crimes