natural lifespan; allotted years
Refers to the full, natural length of a person's life as determined by heaven or fate. Often used in the phrase 天寿を全うする (to live out one's natural life).
My grandfather lived out his natural lifespan and passed away peacefully.
天寿 refers specifically to the natural length of a person's life, while 天命 refers to one's heaven-decreed fate, mission, or destiny, not necessarily lifespan.
Standard kanji spelling; the word is almost always written this way.
Compound of 天 (heaven) and 寿 (longevity). The exact historical derivation is uncertain, but the word has long been used to mean the natural lifespan granted by heaven.