lifespan

noun lifespan

• senescence — growing old; aging.
• senility — the state of being senile, especially the weakness or mental infirmity of old age.
• generation — the entire body of individuals born and living at about the same time: the postwar generation.
• dotage — a decline of mental faculties, especially as associated with old age; senility.
• aged — You use aged followed by a number to say how old someone is.