adjective
biannual (not to be confused with biennial)
Etymology tree Proto-Indo-European *dwóh₁ Proto-Indo-European *dwi- Proto-Italic *dwi- Latin bi-der. Proto-Indo-European *dwóh₁ Proto-Indo-European *dwís Proto-Italic *dwis Old Latin duis Latin bisder. Spanish bi- Spanish anual Spanish bianual From bi- + anual.