noun, noun or participle which takes 'suru', intransitive verb, noun which may take the genitive case particle 'no'
senility; senile decay; infirmity of old age
Refers to the physical and mental decline due to advanced age. Often used in medical or formal contexts, but also in everyday speech. Can be used as a noun, with する to mean 'become senile', or as a no-adjective.
祖父は老衰で亡くなった。
My grandfather died of old age.
老衰が進んで
His senility has progressed, and lately he no longer recognizes his family's faces.