old vs emeritus

old and emeritus both are nouns.

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

old (noun)	emeritus (noun)
past times	a professor or minister who is retired from assigned duties

old (adjective)	emeritus (adjective)
of long duration; not new	honorably retired from assigned duties and retaining your title along with the additional title `emeritus' as in `professor emeritus'
(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