antediluvian vs old

antediluvian and old both are nouns.

Word	Noun	Adjective	Verb	Adverb
antediluvian	Yes	Yes	No	No
old	Yes	Yes	No	No

antediluvian (noun)	old (noun)
a very old person	past times
any of the early patriarchs who lived prior to the Noachian deluge

antediluvian (adjective)	old (adjective)
of or relating to the period before the biblical flood	of long duration; not new
so extremely old as seeming to belong to an earlier period	(used especially of persons) having lived for a relatively long time or attained a specific age
	skilled through long experience
	(used for emphasis) very familiar
	excellent
	just preceding something else in time or order
	belonging to some prior time