years vs senility

years and senility both are nouns.

Word	Noun	Adjective	Verb	Adverb
years	Yes	No	No	No
senility	Yes	No	No	No

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

years: a late time of life
senility: mental infirmity as a consequence of old age; sometimes shown by foolish infatuations

Other hyponyms of years include dotage, second childhood, autumn years, decrepitude.

years (noun)	senility (noun)
a late time of life	the state of being senile
a prolonged period of time	mental infirmity as a consequence of old age; sometimes shown by foolish infatuations
the time during which someone's life continues