ceremony

(noun) a formal event performed on a special occasion. Synonyms: ceremonial, ceremonial occasion, observance. Example: "A ceremony commemorating pearl harbor."

(noun) any activity that is performed in an especially solemn elaborate or formal way. Examples: "The ceremony of smelling the cork and tasting the wine." "He makes a ceremony of addressing his golf ball." "He disposed of it without ceremony."

(noun) the proper or conventional behavior on some solemn occasion. Example: "An inaugural ceremony."