In French, you can say "Au revoir" to say goodbye to an adult.
That is usually "Adiuex" or "Au revoir"
You can say "Au revoir, mon ami" or you can say "Au revoir _______" The blank is the name of your friend.
You say "au revoir"
Au revoir.
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au revoir
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Au revoir
In French, you can say "au revoir" to mean goodbye and "à bientôt" to say see you soon.
You say "au revoir".