adieu
a-dieu
noun
An act of saying goodbye; a formal or final farewell.
"They exchanged their final adieus at the station."
interjection
A formal or literary expression used to say goodbye.
"Adieu, my dear friend, until we meet again."
Thesaurus
Synonyms: sayonara, adios, good-by, good day, au revoir, so long, bye-bye, cheerio, bye, arrivederci, goodbye, auf wiedersehen