dotard vs senior citizen

dotard and senior citizen both are nouns.

Word	Noun	Adjective	Verb	Adverb
dotard	Yes	No	No	No
senior citizen	Yes	No	No	No

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

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

Other hypernyms of dotard include golden ager, old person, oldster.

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