aged / age-old
Two adjectives built on age, with different jobs.
Use aged for a stated number of years, and for something that has been allowed to mature: a man aged 40, aged cheddar. Use age-old for a custom, dispute, or fact that has lasted a very long time: an age-old question. Do not use age-old when you merely mean “old,” and do not use aged as a stand-in for age-old.
Examples
UseThe scholarship is open to students aged 16 to 18.
UseThey revived an age-old method of milling grain.
AvoidThey revived an aged method of milling grain.
As a predicate adjective of people, aged can sound blunt or institutional (the aged). Older or a number is usually kinder and clearer.