Chronological age may differ considerably from a person's functional age.The distinguishing marks of old age normally occur in all five senses at different times and different rates for different persons.
In governmental contexts, it is usually associated with an age at which pensions or medical benefits for the elderly become available.
In commercial contexts, where it may serve as a marketing device to attract customers, the age is often significantly lower.
In Canada, the OAS (Old Age Security) pension is available at 65 (the Conservative government of Stephen Harper had planned to gradually increase the age of eligibility to 67, starting in the years 2023–2029, although the Liberal government of Justin Trudeau is considering leaving it at 65), and the CPP (Canada Pension Plan) as early as age 60.
Old people often have limited regenerative abilities and are more susceptible to disease, syndromes, and sickness than younger adults.
The organic process of ageing is called senescence, Definitions of old age include official definitions, sub-group definitions, and four dimensions as follows. At what age old age begins cannot be universally defined because it differs according to the context.