The word derives from the Venetian phrase s-ciào vostro or s-ciào su literally meaning "I am your slave". This greeting is analogous to the medieval LatinServus which is still used colloquially in parts of Central/Eastern Europe or the antiquated English valediction "Your Obedient Servant." The expression was not a literal statement of fact, but rather a perfunctory promise of good will among friends. The Venetian word for "slave", s-ciào or s-ciàvo, derives from Medieval Latinsclavus, deriving from the ethnic "Slavic", since most of the slaves came from the Balkans. This greeting was eventually shortened to ciào, lost all its servile connotations and came to be used as an informal salutation by speakers of all classes. In modern Italian language, the word is used as an exclamation of resignation, as in Oh, va be', ciao!. A Milanesetongue-twister says Se gh'hinn gh'hinn; se gh'hinn nò, s'ciào.
In contemporary Italian usage, ciao is interchangeable for both an informal hello and goodbye, much like aloha in Hawaiian, salām in Arabic, shalom in Hebrew and ' in Korean. In Italy, ciao is mainly used in informal contexts, i.e. among family members, relatives, and friends, in other words, with those one would address with the familiar tu as opposed to Lei ; in these contexts, ciao can be the norm even as a morning or evening salutation, in lieu of buon giorno or buona sera, deemed too formal among friends, relatives, or the very familiar. In other languages, ciao has come to have more specific meanings. The following list summarizes the spelling and uses of salutations derived from ciao in various languages and countries.
Amharic: ቻው, chaw
Bulgarian: чао, chao
Catalan: ciao, txao
Bosnian: ćao
Czech: ciao, čau and čau čau
Dutch: ciao
English: ciao
Esperanto: ĉaŭ
Estonian: "tšau", also "tšauki" - sometimes pronounced with "s"
Finnish: "tsau", also "tsaukki"
French: ciao, tchao. "Tchao" is slang in French. In 1983, this word was used in the title of the popular movie Tchao, pantin.
German: ciao, tschau
Greek: τσάο, tsao
Hebrew: צ'או chao
Hungarian: csáó or the more informal csá or cső
Interlingua: ciao
Italian: ciao also "ciao ciao".
Japanese: チャオ, chao also チャオチャオ chao chao.
Latvian: čau
Lithuanian: čiau
Macedonian: чао, čao
Malay: چاو دولو, cau dulu ; used informally in Malaysia by the leaving party. The word "cau" can be used informally as a verb which means "leave"
Maltese: ċaw ; also ċaw ċaw
Serbian: ћао, ćao
Polish: ciao
Portuguese: tchau, tchau tchau, or tchauzinho ; in Portugal xau is also used, without the "t" sound, especially in written informal language such as SMS or web chats
Romanian: ciao ; it is often written as ceau although this form is not officially in the Romanian vocabulary
Russian: чау, чао, chao; ; also jokingly - чао-какао, chao-kakao
Croatian: ćao
Sicilian: ciau
Slovak: čau ; mostly as "goodbye", but stands in for "hello" primarily in informal written communication and phone calls because it is more character-efficient/shorter and more hip than the Slovak "ahoj"
Slovene: ciao, čau or čaw ; also čaw čaw
Somali: ciao
Spanish: in Argentina and Uruguay the word chau is the most common expression for "goodbye". In Chile, chao is the standard farewell. In Spain, where "adios" is the common expression, people can use chao as an original way of saying goodbye.
Swiss-German: ciao/Tschau
Tigrinya: ቻው, chaw
Turkish: çav
Venetian: ciào
In some languages, such as Latvian, the vernacular version of ciao has become the most common form of informal salutation. The Vietnamese ' is phonetically similar but not etymologically related.
Variations
The dominant use in Latin America uses the term solely as farewell rather than as a greeting. The greeting has often several variations and minor uses. In Italian and Portuguese, for example, a doubled ciao ciao/tchau tchau means specifically "goodbye", whilst the tripled or quadrupled word means "bye, I'm in a hurry!". Pronounced with a long, it means "hello, I'm so glad/amazed to meet you!" in Italian, and a sarcastic or humorous use of "bye!" in Portuguese. That is not a limited use, as it can also be used in Italian to express sarcasm at another person's point of view about one topic, especially in case that opinion may sound outdated, sì, ciao! meaning "Yeah, right!". In all these cases, however, the special meaning is conferred more by the vocal inflection than by the modified use.