oldness vs senescence

oldness and senescence both are nouns.

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

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

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

oldness (noun)	senescence (noun)
the quality of being old; the opposite of newness	the property characteristic of old age
the opposite of youngness	the organic process of growing older and showing the effects of increasing age