investigate vs investigation

investigate is not a noun while investigation is a noun.

Word	Noun	Adjective	Verb	Adverb
investigate	No	No	Yes	No
investigation	Yes	No	No	No

investigate (noun)	investigation (noun)
	the work of inquiring into something thoroughly and systematically
	an inquiry into unfamiliar or questionable activities

investigate (verb)	investigation (verb)
investigate scientifically
conduct an inquiry or investigation of