investigator vs scientist

investigator and scientist both are nouns.

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

As nouns, scientist is a hypernym of investigator; that is, scientist is a word with a broader meaning than investigator:

investigator (noun)	scientist (noun)
someone who investigates	a person with advanced knowledge of one or more sciences
a scientist who devotes himself to doing research
a police officer who investigates crimes