ciao
n.n. a friendly way to say hello or goodbye in Italian. You use it when you are speaking to someone you know well.
n. a greeting or farewell used in Italian and Italian-American communities. While technically a noun in Italian, it functions as an interjection in English contexts.
I said ciao to my neighbor as I walked past.
The waiter at the local trattoria greeted us with a warm ciao before taking our order.
Borrowed from Italian ciao (“hello, goodbye”), from Venetan ciao (“hello, goodbye, your (humble) servant”), from Venetan s-ciao / s-ciavo (“servant, slave”), from Medieval Latin sclavus (“Slav, slave”), related also to Italian schiavo, English Slav, slave and Old Venetan S-ciavón (“Slav”), from Latin Sclavus, ultimately from Proto-Slavic *slověninъ. Not related to Vietnamese chào (“hello, goodbye”). Doublet of Slav and slave.