Specify 'centenarian' for exact or assumed ages of 100 or more, rather than just old. At the community event, two centenarians were honored for their lifetime achievements.
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Respectful Term
'Centenarian' carries respect for the person's longevity; use it positively. He's a centenarian with incredible stories from the past century.
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Not Derogatory
Unlike some other words for elderly people, 'centenarian' is never used insultingly. Her great-uncle, a sharp-witted centenarian, was the life of the party.