History of Proto-Slavic

The history of Proto-Slavic is the linguistic history of the Proto-Slavic language, the hypothetical ancestor of the modern-day Slavic languages, as it developed from the ancestral Proto-Balto-Slavic language (c. 1500 BC), which is the parent language of the Balto-Slavic languages (both the Slavic and Baltic languages, e.g. Latvian and Lithuanian). The first 2,000 years or so consist of the pre-Slavic era, a long, stable period of gradual development during which the language remained unified, with no discernible dialectal differences. The last stage in which the language remained without internal differences can be dated around 500 AD and is sometimes termed Proto-Slavic proper or Early Proto-Slavic. Following this is the Common Slavic period (c. 500–1000 AD), during which the first dialectal differences appeared but the entire Slavic-speaking area continued to function as a single language, with sound changes tending to spread throughout the entire area. By around 1000 AD, the area had broken up into separate East Slavic, West Slavic and South Slavic languages, and in the following centuries it broke up further into the various modern Slavic languages of which the following are extant: Belarusian, Russian, Rusyn and Ukrainian in the East; Czech, Slovak, Polish, Kashubian and the Sorbian languages in the West, and Bulgarian, Macedonian, Serbo-Croatian and Slovenian in the South.

The period from the early centuries AD to the end of the Common Slavic period around 1000 AD was a time of rapid change, concurrent with the explosive growth of the Slavic-speaking area. By the end of this period, most of the features of the modern Slavic languages had been established. The first historical documentation of the Slavic languages is found in isolated names and words in Greek documents starting in the 6th century AD, when Slavic-speaking tribes first came in contact with the Greek-speaking Byzantine Empire. The first continuous texts date from the late 9th century AD and were written in Old Church Slavonic—based on the language of Thessaloniki in Greek Macedonia—as part of the Christianization of the Slavs by Saints Cyril and Methodius and their followers. Because these texts were written during the Common Slavic period, the language they document is close to the ancestral Proto-Slavic language and is critically important to the linguistic re