A somewhat literary or formal word for one's age, often used in set phrases like 齢を重ねる (to grow older). In casual speech, 年 (とし) or 年齢 (ねんれい) are more common.
At the age of 80, he climbed Mt. Fuji.
Even past the age of eighty, he never misses his daily walk.
齢を重ねるごとに、人生の味わいが深まる。
As one grows older, the richness of life deepens.
My grandfather is still healthy even having reached the age of 90.
年 is the everyday, casual word for someone's age, whereas 齢 sounds old-fashioned or poetic and is reserved for formal or literary contexts.
Standard kanji spelling for 'age' in literary or formal contexts; also used in compounds like 年齢.
Ateji spelling; rarely used and may cause confusion with the common reading は (tooth).
Derived from classical Japanese. The kanji 齢 originally means 'age' or 'years' and is used in compounds like 年齢. The reading よわい is a native Japanese word (yamato-kotoba) with the same meaning.