The dictionary-approved word is longevity, meaning long life or duration of life. It comes from the archaic adjective longevous, which in turn derives from the Latin longaevus, meaning long-lived or ancient. Longetivity does not appear in any of the dictionaries we checked, but as Eric Baković argues in this Language Log post, its existence is not surprising. Words ending in -tivity are more common than words ending in -evity, so longetivity is comfortable to say.
Examples
On the web, longetivity appears about once for every 500 instances of longevity. It even appears in edited publications from time to time—for example:
Tuckman, who turned 108 on Monday, said that if she knew the secret to longetivity, she’d bottle it up and sell it. [Los Angeles Daily News]
Songs from the show don’t seem to have the longetivity of the Liverpool legends’ efforts, however. [NME]
But most major publications use longevity—for example:
The surge has been driven by several factors, including longevity, economics and evolving social mores, according to sociologists. [New York Times]
The north-south divide in longevity is the widest for 40 years and is likely to worsen because of the recession … [The Guardian]
Web longevity is kind of interesting, because the web hasn’t been around that long yet. [Stuff.co.nz]
Obesity likely plays a “significant” role in the U.S.’s smaller longevity gains … [Wall Street Journal]
