from The American Heritage® Dictionary of the English Language, 4th Edition
- interj. Used to express greeting or farewell.
from Wiktionary, Creative Commons Attribution/Share-Alike License
- interj. hello, hi (especially US), howdy (US).
- interj. bye, goodbye.
from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
- n. an acknowledgment that can be used to say hello or goodbye (aloha is Hawaiian and ciao is Italian)
Italian, from dialectal ciau, alteration of Italian (sono vostro) schiavo, (I am your) servant, from Medieval Latin sclavus, slave, servant; see slave.(American Heritage® Dictionary of the English Language, Fourth Edition)
From Italian ciao ("hello, goodbye"), from Venetian ciao ("hello, goodbye, your (humble) servant"), from Venetian s-ciao / s-ciavo ("servant, slave"), from Medieval Latin sclavus ("Slav, slave"), related also to Italian schiavo, English Slav, slave and Old Venetian S-ciavón ("Slav"), from Latin Sclavonia ("Slavonia"). (Wiktionary)