eld vs second childhood

eld and second childhood both are nouns.

Word	Noun	Adjective	Verb	Adverb
eld	Yes	No	No	No
second childhood	Yes	No	No	No

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

eld: a late time of life
second childhood: mental infirmity as a consequence of old age; sometimes shown by foolish infatuations

Other hyponyms of eld include dotage, senility, autumn years, decrepitude.

eld (noun)	second childhood (noun)
a late time of life	mental infirmity as a consequence of old age; sometimes shown by foolish infatuations
a time of life (usually defined in years) at which some particular qualification or power arises