eld vs autumn years

eld and autumn years both are nouns.

Word	Noun	Adjective	Verb	Adverb
eld	Yes	No	No	No
autumn years	Yes	No	No	No

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

eld: a late time of life
autumn years: (literary) the later years of one's life, especially after one has finished their career.

Other hyponyms of eld include dotage, second childhood, senility, decrepitude.

eld (noun)	autumn years (noun)
a late time of life	(literary) the later years of one's life, especially after one has finished their career.
a time of life (usually defined in years) at which some particular qualification or power arises