Investigator
Part of speech: noun
Definition: One who investigates.
Example sentence: An investigator starts research in a new field with faith, a foggy idea, and a few wild experiments. Eventually the interplay of negative and positive results guides the work. By the time the research is completed, he or she knows how it should have been started and conducted.
Detective
Part of speech: noun
Definition: a police officer who looks for evidence as part of solving a crime; an investigator.a person employed to find information not otherwise available to the public.
Example sentence: As a kid, I always wanted to be lots of things. I was a Walter Mitty type. I wanted to be in the French Foreign Legion, a detective, a doctor, a test pilot with a scarf, a fisherman who hauled in a tremendous marlin after a 12-hour fight.