South Slavic language that is the native language of most speakers in Serbia, Montenegro, Bosnia and Herzegovina, and Croatia. It historically served as an important secondary language in Slovenia and Macedonia. The Croats, who are Roman Catholic and who lived for centuries under Venetian or Austro-Hungarian rule, and the Serbs, who are Eastern Orthodox in religion and who, after a short period of independence, lived for five centuries under Turkish domination, have adopted distinct standard (literary) forms, Croatian and Serbian; with the independence of Bosnia and Herzegovina, a Bosnian form must also be recognized. Vocabulary and pronunciation differences exist among the three but form no real barrier to communication. The Croats and Bosnians use the Roman, or Latin, alphabet; the Serbs and Montenegrins use Cyrillic.

The earliest surviving texts in Serbo-Croatian date from the 12th century. The written language in Serbia was a local variant of Church Slavonic (Old Church Slavonic language) until the end of the 17th century, when Russian Church Slavonic was adopted and the compromise style of writing known as Slavono-Serbian began to develop. The modern literary languages are based on the Central dialect, also known as the Shtokavian dialect because the form of the interrogative pronoun “what?” in this dialect is shto (što). It was used in the writings of Vuk Stefanović Karadžić (Karadžić, Vuk Stefanović) (1787–1864), who is also responsible for adapting the Cyrillic alphabet to the sound system of the Serbo-Croatian language. The Latin alphabet was similarly adapted by Ljudevit Gaj (1809–72). The Chakavian dialect (cha 【ča】 = “what?”) can still be heard on the Dalmatian islands and in much of Istria, while the Kajkavian dialect (kaj = “what?”) is spoken in northern Croatia around Zagreb. See also Old Church Slavonic language.