oldness vs staleness

oldness and staleness both are nouns.

Word	Noun	Adjective	Verb	Adverb
oldness	Yes	No	No	No
staleness	Yes	No	No	No

As nouns, staleness is a hyponym of oldness; that is, staleness is a word with a more specific, narrower meaning than oldness:

Other hyponyms of oldness include agedness, senescence, senility, longevity, seniority.

oldness (noun)	staleness (noun)
the quality of being old; the opposite of newness	having lost purity and freshness as a consequence of aging
the opposite of youngness	unoriginality as a result of being dull and hackneyed