Bit is a synonym of Act. Act is related to Marriage. Marriage is related to Promise. Promising is a form of Promise. 
Ceremony is related to Custom. Custom is a type of Practice. Practice is a type of Implementation. 
Bit <--Synonym--> Act <--RelatedTo--> Marriage <--RelatedTo--> Promise <--FormOf-- Promising 
Ceremony <--RelatedTo--> Custom --IsA--> Practice --IsA--> Implementation 