Define “educated” and cite the survey showing how well understood it is among “English speakers” (British English? Commonwealth Nations Generally? N.A. English Speakers? Non-native/ESL?)

I use “fortnightly” to mean “in 2 weeks” because bi-weekly is ambiguous, and while the game is hugely popular I still assume at least 1 person on any email chain with me reads that and is thinking “the fuck does he talk like a Victorian English Dandy for?”