dotard vs old person

dotard and old person both are nouns.

Word	Noun	Adjective	Verb	Adverb
dotard	Yes	No	No	No
old person	Yes	No	No	No

As nouns, old person is a hypernym of dotard; that is, old person is a word with a broader meaning than dotard:

dotard: an oldster in his dotage; someone whose age has impaired his intellect
old person: an elderly person

Other hypernyms of dotard include golden ager, oldster, senior citizen.

dotard (noun)	old person (noun)
an oldster in his dotage; someone whose age has impaired his intellect	an elderly person