years vs decrepitude

years and decrepitude both are nouns.

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

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

years: a late time of life
decrepitude: The quality or state of being wasted and weakened by or as if by the infirmities of old age.

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

years (noun)	decrepitude (noun)
a late time of life	a state of deterioration due to old age or long use
a prolonged period of time	The quality or state of being wasted and weakened by or as if by the infirmities of old age.
the time during which someone's life continues