Dialects of Serbo-Croatian
Kajkavian is spoken in North Croatia, including the capital Zagreb, as well as in a few enclaves in Austria, Hungary, and Romania. Though its speakers are ethnic Croats and Kajkavian is thus generally considered a dialect of Serbo-Croatian, it is closer to neighboring Slovene than it is to Chakavian or Shtokavian. The Kajkavian area of Croatia is bordered on the northwest by Slovene language territory. It is bordered on the east and southeast by Shtokavian dialects roughly along a line that was the former division between Civil Croatia and the Habsburg Military Frontier; in southwest along Kupa and Dobra rivers, it persisted in ancient (medieval) contact with Chakavian dialects.
Serbo-Croatian
In the mid-19th century, Serbian (led by self-taught writer and folklorist Vuk Stefanović Karadžić) and most Croatian writers and linguists (represented by the Illyrian movement and led by Ljudevit Gaj and Đuro Daničić), proposed the use of the most widespread dialect, Shtokavian, as the base for their common standard language. Karadžić standardised the Serbian Cyrillic alphabet, and Gaj and Daničić standardized the Croatian Latin alphabet, on the basis of vernacular speech phonemes and the principle of phonological spelling. In 1850 Serbian and Croatian writers and linguists signed the Vienna Literary Agreement, declaring their intention to create a unified standard. Thus a complex bi-variant language appeared, which the Serbs officially called "Serbo-Croatian" or "Serbian or Croatian" and the Croats "Croato-Serbian", or "Croatian or Serbian". Yet, in practice, the variants of the conceived common literary language served as different literary variants, chiefly differing in lexical inventory and stylistic devices. The common phrase describing this situation was that Serbo-Croatian or "Croatian or Serbian" was a single language. During the Austro-Hungarian occupation of Bosnia and Herzegovina, the language of all three nations was called "Bosnian" until the death of administrator von Kállay in 1907, at which point the name was changed to "Serbo-Croatian".