old vs young

old and young both are nouns.

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

old (noun)	young (noun)
past times	any immature animal
	young people collectively

old (adjective)	young (adjective)
of long duration; not new	(used of living things especially persons) in an early period of life or development or growth
(used especially of persons) having lived for a relatively long time or attained a specific age	(of crops) harvested at an early stage of development; before complete maturity
skilled through long experience	not tried or tested by experience
(used for emphasis) very familiar	being in its early stage
excellent	suggestive of youth; vigorous and fresh
just preceding something else in time or order
belonging to some prior time