Slavic is a group of Indo-European languages spoken in most of eastern Europe, much of the Balkans, parts of central Europe, and the northern part of Asia. The Slavic languages are most closely related to the languages of the Baltic group (Lithuanian, Latvian, and the now-extinct Old Prussian), but they share certain linguistic innovations with the other eastern Indo-European language groups (such as Indo-Iranian and Armenian) as well. From their homeland in east-central Europe (Poland or Ukraine), the Slavic languages have spread to the territory of the Balkans (Bulgarian, Macedonian, Slovene, Serbo-Croatian), central Europe (Czech and Slovak), eastern Europe (Belarusian, Ukrainian, Russian), and the northern parts of Asia (Russian). In addition, Russian is used as a second language by most inhabitants of the countries that were formerly part of the Soviet Union.
Scholars traditionally divide Slavic languages on the basis of geographical and genealogical principle into three main branches, some of which feature subbranches:
East Slavic branch : Old East Slavic (extinct), Old Novgorod (extinct), Ruthenian (extinct), Belarusian, Russian, Ukrainian, Rusyn
West Slavic branch: Czech & Slovak, Czech, Slovak, Lechitic, Old Polish (extinct), Middle Polish (extinct), Polish, Silesian[a], Pomeranian (extinct), Kashubian, Polabian (extinct), Sorbian, Upper Sorbian, Lower Sorbian, Knaanic (extinct)
South Slavic branch: Eastern Group, Old Church Slavonic (extinct), Bulgarian, Macedonian, Church Slavonic, Western Group, Serbo-Croatian, Bosnian, Serbian, Croatian, Montenegrin, Bunjevac, Slovenian
All Slavic languages descend from Proto-Slavic, their immediate parent language, ultimately deriving from Proto-Indo-European, the ancestor language of all Indo-European languages, via a Proto-Balto-Slavic stage. During the Proto-Balto-Slavic period a number of exclusive isoglosses in phonology, morphology, lexis, and syntax developed, which makes Slavic and Baltic the closest related of all the Indo-European branches. The secession of the Balto-Slavic dialect ancestral to Proto-Slavic is estimated on archaeological and glottochronological criteria to have occurred sometime in the period 1500–1000 BCE.
A minority of Baltists maintain the view that the Slavic group of languages differs so radically from the neighboring Baltic group (Lithuanian, Latvian, and the now-extinct Old Prussian), that they could not have shared a parent language after the breakup of the Proto-Indo-European continuum about five millennia ago. Substantial advances in Balto-Slavic accentology that occurred in the last three decades, however, make this view very hard to maintain nowadays, especially when one considers that there was most likely no “Proto-Baltic” language and that West Baltic and East Baltic differ from each other as much as each of them does from Proto-Slavic.
Length, accent, and tone
An area of great difference among Slavic languages is that of prosody (i.e., syllabic distinctions such as vowel length, accent, and tone). Common Slavic had a complex system of prosody, inherited with little change from Proto-Indo-European. This consisted of phonemic vowel length and a free, mobile pitch accent:
All vowels could occur either short or long, and this was phonemic (it could not automatically be predicted from other properties of the word).
There was (at most) a single accented syllable per word, distinguished by higher pitch (as in modern Japanese) rather than greater dynamic stress (as in English).
Vowels in accented syllables could be pronounced with either a rising or falling tone (i.e., there was pitch accent), and this was phonemic.
The accent was free in that it could occur on any syllable and was phonemic.
The accent was mobile in that its position could potentially vary among closely related words within a single paradigm (e.g., the accent might land on a different syllable between the nominative and genitive singular of a given word).
Even within a given inflectional class (e.g., masculine i-stem nouns), there were multiple accent patterns in which a given word could be inflected. For example, most nouns in a particular inflectional class could follow one of three possible patterns: Either there was consistent accent on the root (pattern A), predominant accent on the ending (pattern B), or accent that moved between root and ending (pattern C). In patterns B and C, the accent in different parts of the paradigm shifted not only in location but also type (rising vs. falling). Each inflectional class had its own version of patterns B and C, which might differ significantly from one inflectional class to another.
The modern languages vary greatly in the extent to which they preserve this system. On one extreme, Serbo-Croatian preserves the system nearly unchanged (even more so in the conservative Chakavian dialect); on the other, Macedonian has basically lost the system in its entirety. Between them are found numerous variations:
Slovenian preserves most of the system but has shortened all unaccented syllables and lengthened non-final accented syllables so that vowel length and accent position largely co-occur.
Russian and Bulgarian have eliminated distinctive vowel length and tone and converted the accent into a stress accent (as in English) but preserved its position. As a result, the complexity of the mobile accent and the multiple accent patterns still exists (particularly in Russian because it has preserved the Common Slavic noun inflections, while Bulgarian has lost them).
Czech and Slovak have preserved phonemic vowel length and converted the distinctive tone of accented syllables into length distinctions. Phonemic accent is otherwise lost, but the former accent patterns are echoed to some extent in corresponding patterns of vowel length/shortness in the root. Paradigms with mobile vowel length/shortness do exist but only in a limited fashion, usually only with the zero-ending forms (nom. sg., acc. sg., and/or gen. pl., depending on inflectional class) having a different length from the other forms. (Czech has a couple of other “mobile” patterns, but they are rare and can usually be substituted with one of the “normal” mobile patterns or a non-mobile pattern.)
Old Polish had a system very much like Czech. Modern Polish has lost vowel length, but some former short-long pairs have become distinguished by quality (e.g., [o oː] > [o u]), with the result that some words have vowel-quality changes that exactly mirror the mobile-length patterns in Czech and Slovak.