dotard vs oldster

dotard and oldster both are nouns.

Word	Noun	Adjective	Verb	Adverb
dotard	Yes	No	No	No
oldster	Yes	No	No	No

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

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

Other hypernyms of dotard include golden ager, old person, senior citizen.

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