Shtokavian or Štokavian (ʃtɒˈkɑːviən,_-ˈkæv-; štokavski / штокавски, ʃtǒːkaʋskiː) is the prestige supradialect of the pluricentric Serbo-Croatian language and the basis of its Serbian, Croatian, Bosnian and Montenegrin standards. It is a part of the South Slavic dialect continuum. Its name comes from the form for the interrogative pronoun for "what" što (Western Shtokavian; it is šta in Eastern Shtokavian). This is in contrast to Kajkavian and Chakavian (kaj and ča also meaning "what").
Shtokavian is spoken in Serbia, Montenegro, Bosnia and Herzegovina, much of Croatia, and the southern part of Austria's Burgenland. The primary subdivisions of Shtokavian are based on three principles: one is different accents whether the subdialect is Old-Shtokavian or Neo-Shtokavian, second is the way the old Slavic phoneme jat has changed (Ikavian, Ijekavian or Ekavian), and third is presence of Young Proto-Slavic isogloss (Schakavian or Shtakavian). Modern dialectology generally recognises seven Shtokavian subdialects.
The early medieval Slavs who later spoke various Bulgarian and Serbo-Croatian dialects migrated across Moldavia and Pannonia. According to Frederik Kortlandt, the shared innovations originate from "Trans-Carpathian" homeland, and by the 4th and 6th century, "the major dialect divisions of Slavic were already established". Dialectologists and Slavists maintain that when the separation of Western South Slavic speeches happened, they separated into five divergent groups, more specifically two, one Slovene and second Serbo-Croatian with four divergent groups - Kajkavian, Chakavian, Western Shtokavian and Eastern Shtokavian. The latter group can be additionally divided into first (Kajkavian, Chakavian, Western Shtokavian) and second (Eastern Shtokavian, Torlakian). As noted by Ranko Matasović, "the Shtokavian dialect, on the other hand, was from the earliest times very non-unique, with the Western Shtokavian dialects leaning towards Kajkavian, and the Eastern Shtokavian to Torlakian".