ancient vs antediluvian

ancient and antediluvian both are nouns.

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

As nouns, ancient and antediluvian are synonyms defined as:

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

ancient (adjective)	antediluvian (adjective)
very old	of or relating to the period before the biblical flood
belonging to times long past especially of the historical period before the fall of the Western Roman Empire	so extremely old as seeming to belong to an earlier period