prehistoric vs prehistory

prehistoric is not a noun while prehistory is a noun.

Word	Noun	Adjective	Verb	Adverb
prehistoric	No	Yes	No	No
prehistory	Yes	No	No	No

prehistoric (noun)	prehistory (noun)
	the time during the development of human culture before the appearance of the written word

prehistoric (adjective)	prehistory (adjective)
of or relating to times before written history
belonging to or existing in times before recorded history
outdated