oldness vs longevity

oldness and longevity both are nouns.

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

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

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

oldness (noun)	longevity (noun)
the quality of being old; the opposite of newness	duration of service
the opposite of youngness	the property of being long-lived