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senile

senile /ˈsiːˌnajəl/ adjective
senile
/ˈsiːˌnajəl/
adjective
Britannica Dictionary definition of SENILE
[more senile; most senile]
: showing a loss of mental ability (such as memory) in old age

— senility

/sɪˈnɪləti/ noun [noncount]