senility vs dotage

senility and dotage both are nouns.

Word	Noun	Adjective	Verb	Adverb
senility	Yes	No	No	No
dotage	Yes	No	No	No

As nouns, senility and dotage are synonyms defined as:

senility and dotage: mental infirmity as a consequence of old age; sometimes shown by foolish infatuations

Other synonyms of senility include second childhood.

senility (noun)	dotage (noun)
the state of being senile	mental infirmity as a consequence of old age; sometimes shown by foolish infatuations
mental infirmity as a consequence of old age; sometimes shown by foolish infatuations