Bye-bye in Italian can be expressed in three different ways. The first is 'CIAO' which is the most common and informal way to say goodbye in Italian. It is derived from the Venetian word 's-ciào' which means 'SERVANT'. The second is 'ADIOS', which is a Spanish word that has been adopted into Italian. It is derived from the Latin phrase 'ad deum' which means 'to God'. The third is 'ADIEU', which is a French word that has also been adopted into Italian. It is derived from the Old French phrase 'a dieu vous comant' which means 'I commend you to God'.