senility

noun

1. (uncountable)The bodily and mental deterioration associated with old age: Synonym of senescence.

   “Near-synonym: second childhood”

2. (uncountable)The losing of memory and reason due to senescence.

   “He was entering his years of senility and not liking it a bit.”

3. (archaic, countable)An elderly, senile person.

   “There was no need for George Playford to talk as if they were doddering senilities.”