vicennial /vī-senˈyəl/

1. Lasting, or coming at the end of, twenty years
2. Occurring every twenty years

• positronium
• positroniums
• positrons
• posits
• posnet
• posnets
• posological
• posologies
• posology
• poss
• posse
• posse comitatus
• possed
• posser
• possers
• posses
• possess
• possessable
• possessed
• possesses
• possessing
• possession
• possessional
• possessionary
• possessionate