Sometimes the footnotes are the best part

 

  1. By convention, “biweekly” should mean “every two weeks”. Unfortunately, the bi- suffix has been misunderstood so frequently to mean “twice per” instead of “every two” that “biweekly” now uselessly means “every two weeks” or “twice per week”.

    The semi- prefix properly, and only, means “twice per”. Therefore, the correct word for “twice per week” is “semiweekly”. But since misunderstandings of this have ruined bi-, there’s now no English word2 that unambiguously means “every two weeks”.

    I’m using “biweekly” to properly mean “every two weeks” in protest of this widespread definition-shifting vocabularly ignorance. 

  2. Except “fortnightly”, which is ridiculous. 

     marco.org