A slowly progressing decline in physical and mental health, apparently as a result of natural causes resulting from the processes of aging: Karen was worried about the senile deterioration of her neighbor who was almost 90 years old and was no longer able to go for walks without hanging on to her daughter's arm.

Mike's neighbor, who was 85 and formerly an Olympic swimmer, apologized because he figured that his senile deterioration was limiting him to swim 29 laps; while his younger neighbor, who is 55 years old, thought he was doing pretty good when he could swim nine laps.