old vs antediluvian

old and antediluvian both are nouns.

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

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

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