investigate vs search

investigate is not a noun while search is a noun.

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

As verbs, search is a hyponym of investigate; that is, search is a word with a more specific, narrower meaning than investigate:

Other hyponyms of investigate include explore, research, explore, examine, probe, research, experiment.

investigate (noun)	search (noun)
	the activity of looking thoroughly in order to find something or someone
	boarding and inspecting a ship on the high seas
	an investigation seeking answers
	the examination of alternative hypotheses
	an operation that determines whether one or more of a set of items has a specified property

investigate (verb)	search (verb)
investigate scientifically	inquire into
conduct an inquiry or investigation of	try to locate or discover, or try to establish the existence of
	subject to a search
	search or seek