centenarian
Refers to a person who is 100 years old or older. A formal term often used in official contexts, such as government statistics or congratulatory messages.
In Japan, the number of centenarians is increasing year by year.
My grandmother will become a centenarian next month.
Compound of 百 (hundred), 寿 (longevity, congratulations), and 者 (person). The term is a modern coinage reflecting the celebration of reaching 100 years of age.