History of Proto-Slavic

See also: Proto-Slavic and History of the Slavic languages

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 period during which none of the later dialectal differences between Slavic languages had yet happened. The last stage in which the language remained without internal differences that later characterize different Slavic languages 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 Slavic dialect used in the region 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 still presenting enough unity, therefore it is critically important to the linguistic reconstruction of Slavic-language history.

This article covers historical developments up through the end of the Common Slavic period. For later developments, see History of the Slavic languages.

Introduction

Proto-Slavic is descended from Proto-Balto-Slavic (the ancestor of the Balto-Slavic languages). This language in turn is descended from Proto-Indo-European, the parent language of the vast majority of European languages (including English, German, Spanish, French, etc.). Proto-Slavic gradually evolved into the various Slavic languages during the latter half of the first millennium AD, concurrent with the explosive growth of the Slavic-speaking area. There is no scholarly consensus concerning either the number of stages involved in the development of the language (its periodization) or the terms used to describe them. For consistency and convenience, this article and the Proto-Slavic article adopt the following scheme:

1. Pre-Slavic (c. 1500 BC — 300 AD): A long period of gradual development. The most significant phonological developments during this period involved the prosodic system, e.g. tonal and other register distinctions on syllables.
2. Proto-Slavic proper or Early Common Slavic (c. 300 — 600 AD): The early, uniform stage of Common Slavic, a period of rapid phonological change. There are no dialectal distinctions reconstructible from this period.
3. Middle Common Slavic (c. 600 — 800 AD): The stage with the earliest identifiable dialectal distinctions. Rapid phonological change continued, although with the massive expansion of the Slavic-speaking area. Although some dialectal variation did exist, most sound changes were still uniform and consistent in their application. By the end of this stage, the vowel and consonant phonemes of the language were largely the same as those still found in the modern languages. For this reason, reconstructed "Proto-Slavic" forms commonly found in scholarly works and etymological dictionaries normally correspond to this period.
4. Late Common Slavic (c. 800 — 1000 AD, although perhaps through c. 1150 AD in Kievan Rus', in the far northeast): The last stage in which the whole Slavic-speaking area still functioned as a single language, with sound changes normally propagating throughout the entire area, although often with significant dialectal variation in the details.

Slavic scholars differ widely in both the terminology and periodization of these developments. Some scholars do not use the term "Common Slavic" at all. For some others, the Common Slavic period comes after Proto-Slavic rather than including it. Some scholars (e.g. Frederik Kortlandt) divide the Common Slavic period into five or more stages, while others use as few as two (an early, uniform stage and a late, dialectally differentiated stage).

Origin

Area of Balto-Slavic dialect continuum (purple) with proposed material cultures correlating to speakers of Balto-Slavic in the Bronze Age (white). Red dots = archaic Slavic hydronyms

Proto-Balto-Slavic

The currently most favoured model, the Kurgan hypothesis, places the Urheimat of the Proto-Indo-European people in the Pontic steppe, represented archaeologically by the 5th millennium BCE Sredny Stog culture. From here, various daughter dialects dispersed radially in several waves between c. 4400 BCE and 3000 BCE. The phonological changes which set Balto-Slavic apart from other Indo-European languages probably lasted from c. 3000 to 1000 BCE, a period known as common Proto-Balto-Slavic. Kortlandt (1990) links the earliest stages of Balto-Slavic development with the Middle Dnieper culture which connects the Corded Ware and Yamna cultures. Kurganists connect the latter two cultures with the so-called "Northwest (IE) group" and the Iranian-speaking steppe nomads, respectively. This fits with the linguistic evidence in that Balto-Slavic appears to have had close contacts with Indo-Iranian and Proto-Germanic.

Scholars have proposed an association between Balto-Slavic and Germanic on the basis of lexical and morphological similarities that are unique to these languages. Apart from a proposed genetic relationship (PIE forming a Germano-Balto-Slavic sub-branch), the similarities are likely due to continuous contacts, whereby common loan words spread through the communities in the forest zones at an early time of their linguistic development.

Similarly, Balto-Slavic and Indo-Iranian might have formed some kind of continuum from the north-west to the south-east, given that they share both satemization and the Ruki sound law. On the other hand genetic studies have shown that Slavs and North Indians share much larger amounts of the R1a haplogroup (associated with the spread of Indo-European languages) than do most Germanic populations. The Balto-Slavic - Indo-Iranian link might thus be a result of a large part of common ancestry, between Eastern Europeans and Indo-Iranians. Balto-Slavic then expanded along the forest zone, replacing earlier centum dialects, such as Pre-Proto-Germanic. This might explain the presence of a few prehistoric centum adstratal lexemes.

Pre-Slavic

A pre-Slavic period began c. 1500 to 1000 BCE, whereby certain phonological changes and linguistic contacts did not disperse evenly through all Balto-Slavic dialects. The development into Proto-Slavic probably occurred along the southern periphery of the Proto-Balto-Slavic continuum. The most archaic Slavic hydronyms are found here, along the middle Dnieper, Pripet and upper Dniester rivers. This agrees well with the fact that inherited Common Slavic vocabulary does not include detailed terminology for physical surface features peculiar of the mountains or the steppe, nor any relating to the sea, to coastal features, littoral flora or fauna, or salt water fishes. On the other hand, it does include well-developed terminology for inland bodies of water (lakes, river, swamps) and kinds of forest (deciduous and coniferous), for the trees, plants, animals and birds indigenous to the temperate forest zone, and for the fish native to its waters. Indeed, Trubachev argues that this location fostered contacts between speakers of Pre-Proto-Slavic with the cultural innovations which emanated from central Europe and the steppe. Although language groups cannot be straightforwardly equated with archaeological cultures, the emergence of a Pre-Proto-Slavic linguistic community corresponds temporally and geographically with the Komarov and Chernoles cultures (Novotna, Blazek). Both linguists and archaeologists therefore often locate the Slavic Urheimat specifically within this area.

Historical distribution of the Slavic languages. The larger shaded area is the Prague-Penkov-Kolochin complex of cultures of the sixth to seventh centuries, likely corresponding to the spread of Slavic-speaking tribes of the time. The smaller shaded area indicates the core area of Slavic river names (after Mallory & Adams (1997:524ff).

In proto-historical times, the Slavic homeland experienced intrusions of foreign elements. Beginning from c. 500 BCE to 200 CE, the Scythians and then the Sarmatians expanded their control into the forest steppe. A few Eastern Iranian loan words, especially relating to religious and cultural practices, have been seen as evidence of cultural influences. Subsequently, loan words of Germanic origin also appear. This is connected to the movement of east Germanic groups into the Vistula basin, and subsequently to the middle Dnieper basin, associated with the appearance of the Przeworsk and Chernyakhov cultures, respectively.

Despite these developments, Slavic remained conservative and was still typologically very similar to other Balto-Slavic dialects. Even into the Common Era, the various Balto-Slavic dialects formed a dialect continuum stretching from the Vistula to the Don and Oka basins, and from the Baltic and upper Volga to southern Russia and northern Ukraine. Exactly when Slavs began to identify as a distinct ethno-cultural unit remains a subject of debate. For example, Kobylinski (2005) links the phenomenon to the Zarubinets culture 200 BCE to 200 CE, Vlodymyr Baran places Slavic ethnogenesis within the Chernyakov era, while Curta places it in the Danube basin in the sixth century CE. It is likely that linguistic affinity played an important role in defining group identity for the Slavs. The term Slav is proposed to be an autonym referring to "people who (use the words to) speak."

Another important aspect of this period is that the Iranian dialects of the Scythians and Sarmatians had a considerable impact on the Slavic vocabulary, during the extensive contacts between the aforementioned languages and (early) Proto-Slavic for about a millennium, and the eventual absorption and assimilation (e.g. Slavicisation) of the Iranian-speaking Scythians, Sarmatians, and Alans in Eastern Europe by the Proto-Slavic population of the region.

Proto-Slavic and Common Slavic (c. 400–1000 AD)

Beginning around 500 AD, the Slavic speakers rapidly expanded in all directions from a homeland in eastern Poland and western Ukraine. As it expanded throughout eastern Europe, it obliterated whatever remained of easternmost Celtic, Avar, Venetic, possibly Dacian, as well as many other Balto-Slavic dialects, and the Slav ethnonym spread out considerably. By the eighth century AD, Proto-Slavic is believed to have been spoken uniformly from Thessaloniki to Novgorod.

What caused the rapid expansion of Slavic remains a topic of discussion. Traditional theories link its spread to a demographic expansion of Slavs migrating radially from their Urheimat, whereas more processual theories attempt to modify the picture by introducing concepts such as "elite dominance" and "language shifts.". Literary and archaeological evidence suggests that eastern European barbaricum in the 6th century was linguistically and culturally diverse, somewhat going against the idea of a large demographic expansion of an ethnically homogeneous Slavic people. Instead, Proto-Slavic might have been lingua franca among the various barbarian ethnicities that emerged in the Danubian, Carpathian and steppe regions of Europe after the fall of the Hun Empire, such as the Sklaveni, Antes, and Avars. Cultural contacts between emerging societal elites might have led to the "language of one agricultural community spread(ing) to other agricultural societies." This has been substantiated archaeologically, seen by the development of networks which spread of "Slavic fibulae," artifacts representing social status and group identity. Horace Lunt argues that only as a lingua franca could Slavic have remained mutually intelligible over vast areas of Europe, and that its disintegration into different dialects occurred after the collapse of the Avar khanate. However, even proponents of this theory concede that it fails to explain how Slavic spread to the Baltic and western Russia, areas which had no historical connection with the Avar Empire. Whatever the case, Johanna Nichols points out that the expansion of Slavic was not just a linguistic phenomenon, but the expansion of an ethnic identity.

Due to incompletely understood sociocultural factors, a number of sound changes occurred that uniformly affected all later dialects even well after the Slavic-speaking area had become dialectally differentiated, for at least four or five centuries after the initial Slavic dispersion. This makes it difficult to identify a single point at which Proto-Slavic broke up into regional dialects. As a result, it is customary to speak of a "Common Slavic" period during which sound changes spread across the entire Slavic-speaking area, but not necessarily with uniform results. The Early Common Slavic period, from roughly 400 to 600 AD, can be identified as Proto-Slavic proper. The onomastic evidence and glosses of Slavic words in foreign-language texts show no detectable regional differences during this period.

During the Middle Common Slavic period, from perhaps 600 to 800 AD, some dialectal differences existed, especially in peripheral dialects, but most sound changes still occurred uniformly. (For example, the Old Novgorod dialect did not exhibit the second palatalization of velars while all the other Slavic dialects did.) Reconstructed "Proto-Slavic" forms are normally from this period. It is thought that the distinction of long and short vowels by quality, normally reflected in "Proto-Slavic" reconstructed forms, occurred during this time: Greek transcriptions from the 5th and 6th centuries AD still indicate Common Slavic *o as a.

During the Late Common Slavic period, from c. 800 to 1000 AD, conceptual sound changes (e.g. the conversion of TORT sequences into open syllables and the development of the neoacute accent) still occurred across the entire Slavic area, but often in dialectally differentiated ways. In addition, migrations of Uralic and Romance speaking peoples into modern Hungary and Romania created geographic separations between Slavic dialects. Written documents of the ninth, tenth and eleventh centuries demonstrate some local features. For example, the Freising monuments show a dialect which contains some phonetic and lexical elements peculiar to Slovenian dialects (e.g. rhotacism, the word krilatec). Significant continuous Slavic-language texts exist from this period, beginning with the extant Old Church Slavonic (OCS) texts, composed in the 9th century but copied in the 10th century. The end of the Common Slavic period is usually reckoned with the loss of weak yers, which occurred in Bulgaria c. 950 AD but did not reach Russia until c. 1150 AD. This is clearly revealed in the texts themselves: During the century or so between the composition and copying of the OCS texts, the weak yers disappeared as vowels, and as a result, the texts show marked instability in their representation. (The main exception is the Codex Zographensis, copied just before yer loss.) On the other hand, the Old East Slavic texts represent the weak yers with almost complete etymological fidelity until nearly two centuries later.

The terminology of these periods is not consistent. For example, Schenker speaks only of "Early Proto-Slavonic" (= Early Common Slavic, the period of entirely uniform developments) and "Late Proto-Slavonic" (= Middle and Late Common Slavic), with the latter period beginning with the second regressive palatalization, due to the differing outcomes of pre-Proto-Slavic *x. (Note that some authors, e.g. Kortlandt, place the beginning of dialectal developments later by postulating an outcome *ś of the second regressive palatalization, which only later developed into *s or *š.) Kortlandt's chronology, on the other hand, includes six stages after the Balto-Slavic period:

1. "Early Slavic" (≈ pre-Proto-Slavic)
2. "Early Middle Slavic" (≈ Early Common Slavic)
3. "Late Middle Slavic" (≈ Middle Common Slavic)
4. "Young Proto-Slavic" (≈ first part of Late Common Slavic)
5. "Late Proto-Slavic" (≈ second part of Late Common Slavic)
6. "Disintegrating Slavic" (widespread post-Common-Slavic developments, e.g. loss of nasalization)

The first regressive palatalization of velars (see below) may well have operated during Early Common Slavic and is thought by Arnošt Lemprecht to have specifically operated during the 5th century AD. The progressive palatalization of velars, if it is older, can predate this only by 200–300 years at most, since it post-dates Proto-Germanic borrowings into Slavic, which are generally agreed to have occurred no earlier than the 2nd century AD. The monophthongization of /au/, /ai/ is thought to have occurred near the end of Early Common Slavic or beginning of Middle Common Slavic (c. 600 AD), and the second regressive palatalization of velars not long afterwards. This implies that, until around the time of the earliest Slavic expansion, Slavic was a conservative language not so different from the various attested Baltic languages.

First written Slavic languages

In the second half of the ninth century, the Slavic dialect spoken north of Thessaloniki, in the hinterlands of Macedonia, became the basis for the first written Slavic language, created by the brothers Cyril and Methodius who translated portions of the Bible and other church books. The language they recorded is known as Old Church Slavonic. Old Church Slavonic is not identical to Proto-Slavic, having been recorded at least two centuries after the breakup of Proto-Slavic, and it shows features that clearly distinguish it from Proto-Slavic. However, it is still reasonably close, and the mutual intelligibility between Old Church Slavonic and other Slavic dialects of those days was proved by Cyril and Methodius' mission to Great Moravia and Pannonia. There, their early South Slavic dialect used for the translations was clearly understandable to the local population which spoke an early West Slavic dialect.

Notation

Main article: Proto-Balto-Slavic language § Notation

See Proto-Balto-Slavic language#Notation for much more detail on the uses of the most commonly encountered diacritics for indicating prosody (á, à, â, ã, ȁ, a̋, ā, ă) and various other phonetic distinctions (ą, ẹ, ė, š, ś, etc.) in different Balto-Slavic languages.

Vowel notation

Two different and conflicting systems for denoting vowels are commonly in use in Indo-European and Balto-Slavic linguistics on one hand, and Slavic linguistics on the other. In the first, vowel length is consistently distinguished with a macron above the letter, while in the latter it is not clearly indicated. The following table explains these differences:

Vowel	IE/B-S	Slavic
Short front closed vowel (front yer)	i	ĭ or ь
Short back closed vowel (back yer)	u	ŭ or ъ
Short back open vowel	a	o
Long front closed vowel	ī	i
Long back closed vowel	ū	y [ɪ:]
Long front open vowel (yat)	ē	ě
Long back open vowel	ā	a

For consistency, all discussions of sounds up to (but not including) Middle Common Slavic use the common Balto-Slavic notation of vowels, while discussions of Middle and Late Common Slavic (the phonology and grammar sections) and later dialects use the Slavic notation.

Other vowel and consonant diacritics

Other marks used within Balto-Slavic and Slavic linguistics are:

• The haček on consonants (č š ž), indicating a "hushing" quality [tʃ ʃ ʒ], as in English kitchen, mission, vision.
• Various strongly palatal(ized) consonants (a more "hissing" quality) usually indicated by an acute accent (ć ǵ ḱ ĺ ń ŕ ś ź) or a haček (ď ľ ň ř ť).
• The ogonek (ą ę ǫ), indicating vowel nasalization (in modern standard Lithuanian this is historic only).

Prosodic notation

For Middle and Late Common Slavic, the following marks are used to indicate prosodic distinctions, based on the standard notation in Serbo-Croatian:

• Long rising (á): This indicates the Balto-Slavic acute accent in Middle Common Slavic only.
• Short rising (à): This indicates the Balto-Slavic acute accent in Late Common Slavic, where it was shortened.
• Long falling (ȃ): This normally indicates the Balto-Slavic circumflex accent. In Late Common Slavic, it also indicates originally short (falling) accent that was lengthened in monosyllables. This secondary circumflex occurs only on the short vowels e, o, ь, ъ in an open syllable (i.e. when not forming part of a liquid diphthong).
• Short falling (ȁ): This indicates the Balto-Slavic short accent. In Late Common Slavic, this accent was lengthened in monosyllables (see preceding entry).
• Neoacute (ã): This indicates the Late Common Slavic neoacute accent, which was pronounced as a rising accent, usually long but short when occurring on some syllable types in certain languages. This results from retraction of the accent, i.e. the Middle Common Slavic accent fell on the following syllable (usually specifically a weak yer).

Other prosodic diacritics

There are unfortunately multiple competing systems used to indicate prosody in different Balto-Slavic languages (see Proto-Balto-Slavic language#Notation for more details). The most important for this article are:

1. Three-way system of Proto-Slavic, Proto-Balto-Slavic, modern Lithuanian: Acute tone (á) vs. circumflex tone (ȃ or ã) vs. short accent (à).
2. Four-way Serbo-Croatian system, also used in Slovenian and often in Slavic reconstructions: long rising (á), short rising (à), long falling (ȃ), short falling (ȁ). In the Chakavian dialect and other archaic dialects, the long rising accent is notated with a tilde (ã), indicating its normal origin in the Late Common Slavic neoacute accent (see above).
3. Length only, as in Czech and Slovak: long (á) vs. short (a).
4. Stress only, as in Russian, Ukrainian and Bulgarian: stressed (á) vs. unstressed (a).

Historical development up to Proto-Slavic

See also: Proto-Slavic and Proto-Balto-Slavic language

Split from Indo-European

Proto-Balto-Slavic has the satem sound changes wherein Proto-Indo-European (PIE) palatovelar consonants became affricate or fricative consonants pronounced closer to the front of the mouth, conventionally indicated as *ś and *ź. These became simple dental fricatives *s and *z in Proto-Slavic:

• *ḱ → *ś → *s
• *ǵ → *ź → *z
• *ǵʰ → *ź → *z

This sound change was incomplete, in that all Baltic and Slavic languages have instances where PIE palatovelars appear as *k and *g, often in doublets (i.e. etymologically related words, where one has a sound descended from *k or *g and the other has a sound descended from *ś or *ź).

Other satem sound changes are delabialization of labiovelar consonants before rounded vowels and the ruki sound law, which shifted *s to *š after *r, *u, *k or *i. In Proto-Slavic, this sound was shifted backwards to become *x, although it was often shifted forward again by one of the three sound laws causing palatalization of velars.

In the Balto-Slavic period, final *t and *d were lost.

Also present in Balto-Slavic were the diphthongs *ei and *ai as well as liquid diphthongs *ul, *il, *ur, *ir, the latter set deriving from syllabic liquids; the vocalic element merged with *u after labiovelar stops and with *i everywhere else, and the remaining labiovelars subsequently lost their labialization.

Around this time, the PIE aspirated consonants merged with voiced ones:

• *bʰ → *b
• *dʰ → *d
• *gʰ → *g

Once it split off, the Proto-Slavic period probably encompassed a period of stability lasting 2000 years with only several centuries of rapid change before and during the breakup of Slavic linguistic unity that came about due to Slavic migrations in the early sixth century. As such, the chronology of changes including the three palatalizations and ending with the change of *ě to *a in certain contexts defines the Common Slavic period.

Long *ē and *ō raised to *ī and *ū before a final sonorant, and sonorants following a long vowel were deleted. Proto-Slavic shared the common Balto-Slavic merging of *o with *a. However, while long *ō and *ā remained distinct in Baltic, they merged in Slavic, so that early Slavic did not possess the sounds *o or *ō.

Changes in syllable structure

Eastern Europe in the 3rd century CE:

  Chernyakhov culture

  Przeworsk culture

  Wielbark Culture (associated with the Goths)

  a Baltic culture (Aesti/Yotvingian?)

  Debczyn culture

  Roman Empire

A tendency for rising sonority in a syllable (arrangement of phonemes in a syllable from lower to higher sonority) marks the beginning of the Common Slavic period. One aspect of this, generally referred to as the "Law of Open Syllables", led to a gradual elimination of closed syllables. When possible, syllable-final consonants were resyllabified into the following syllable. For example, *kun-je-mou "to him" became *ku-nje-mou (OCS kъňemu), and *vuz-dā-tēi "to give back" became *vu-zdā-tēi (OCS vъzdati). This entailed no actual phonetic change, but simply a reinterpretation of syllable boundaries, and was possible only when the entire cluster could begin a syllable or word (as in *nj, *zd, *stv, but not *nt, *rd, *pn). In other cases, syllable-final obstruents were either deleted (e.g. OCS sъnъ "sleep" < PIE *supnos); diphthongs were monophthongized; nasal consonants in the syllable coda were reduced to nasalization of the preceding vowel (*ę and *ǫ); and liquid diphthongs were eliminated by metathesis (e.g. *or → *ro), epenthesis (e.g. *or → *oro), or conversion to syllabic sonorants (e.g. *ur → *ṛ).

Another tendency arose in the Common Slavic period wherein successive segmental phonemes in a syllable assimilated articulatory features (primarily place of articulation). This is called syllable synharmony or intrasyllabic harmony. Thus syllables (rather than just the consonant or the vowel) were distinguished as either "soft" (palatal) or "hard" (non-palatal). This led to consonants developing palatalized allophones in syllables containing front vowels, resulting in the first regressive palatalization. It also led to the fronting of back vowels after /j/.

After these changes, a CV syllable structure (that is, one of segments ordered from lower to higher sonority) arose and the syllable became a basic structural unit of the language.

Nasalization

Syllable-final nasals *m and *n (i.e. when not directly followed by a vowel) coalesced with a previous vowel, causing it to become nasalized:

Late PIE	Early Proto-Slavic	Proto-Slavic	Common Slavic
*am, *an, *ām, *ān	*ą̄		*ǫ
*em, *en, *ēm, *ēn	ę̄		*ę
*im, *in, *īm, *īn	į̄	ę̄	*ę
*um, *un, *ūm, *ūn	*ų̄		*y
*Jum, *Jun, *Jūm, *Jūn	*Jų̄	*Jį̄	*Ję̇

Note that in Balto-Slavic studies, the ogonek diacritic is normally used to indicate nasalization (ą, ǫ, ę, etc.) rather than the IPA-standard tilde (/ã õ ẽ/ etc.). The tilde is instead used to indicate a particular type of tone on the vowel. (Which tone is indicated varies depending on the language in question. See the notation section above.)

The nasal element of *im, *in, *um, *un is lost word-finally in inflectional endings, and therefore does not cause nasalization.

Examples showing these developments:

Late PIE	Balto-Slavic	Meaning	Lithuanian	Proto-Slavic	Late Common Slavic
*ǵómbʰos	*źambas	"tooth"	žam̃bas "sharp edge"	*zą̄̂bu	*zǫ̂bъ
*ǵenh₃tis	*źénˀtis, *źénˀtas	"son in law"	žéntas	*zę̄́tu	*zę̀tъ
*deḱmtos	*deśimtas	"tenth"	dešim̃tas	*desę̄tu	*desętъ
*lnHkom	*lúnˀka	"bast"	lùnkas	*lų̄́ka	*lỳko
?	*kanjun(s)	"horses" (acc.)	—	*kanjį̄	*koňę̇

The nasalization of *ų̄ was eventually lost. However, when *ų̄ followed a palatal consonant such as /j/ (indicated generically as *J), it was fronted to *į̄, which preserved its nasalization much longer. This new *į̄ did not originally merge with the result of nasalizing original *im/*in, as shown in the table. Instead, it evolved in Common Slavic times to a high-mid nasal vowel *ę̇, higher than the low-mid vowel *ę. In South Slavic, these two vowels merged as *ę. Elsewhere, however, *ę̇ was denasalized, merging with *ě, while *ę was generally lowered to *æ̨ (often reflected as ja). Common Slavic *desętyję̇ koňę̇ "the tenth horse (accusative)" appears as desętyję konę in Old Church Slavonic and desete konje in Serbo-Croatian (South Slavic), but as desátý koně in modern Czech and dziesiąte konie in Polish (West Slavic), and as десятые кони (desjatyje koni) in Russian (East Slavic). Note that Polish normally preserves nasal vowels, but it does not have a nasal vowel in the accusative plural ending, while it retains it in the stem of "tenth".

Nasalization also occurred before a nasal consonant, whenever a vowel was followed by two nasals. However, in this case, several later dialects denasalized the vowel at an early date. Both pomęnǫti and poměnǫti "remember" (from earlier *pa-men-nantī?) are found in Old Church Slavonic. The common word *jĭmę "name" can be traced back to earlier *inmen with denasalization, from a PIE zero grade alternant *h₁n̥h₃mén-.

First regressive palatalization

Main article: Slavic first palatalization

As an extension of the system of syllable synharmony, velar consonants were palatalized to postalveolar consonants before front vowels (*i, *ī, *e, *ē) and before *j:

• *k → *č [tʃ]
• *g → *dž [dʒ] → *ž [ʒ]
• *x → *š [ʃ]
• *sk → *šč [ʃtʃ]
• *zg → *ždž [ʒdʒ]

This was the first regressive palatalization. Although *g palatalized to an affricate, this soon lenited to a fricative (but *ždž was retained). Some Germanic loanwords were borrowed early enough to be affected by the first palatalization. One example is *šelmŭ, from earlier *xelmŭ, from Germanic *helmaz.

Iotation

In a process called iotation or yodization, *j merged with a previous consonant (unless it was labial), and those consonants acquired a palatal articulation. Compare English yod-coalescence. This change probably did not occur together with the first regressive palatalization, but somewhat later, and it remained productive well into the Late Common Slavic period.

• *tj → *ť
• *dj → *ď
• *stj → *šť (→ presumably šč)
• *zdj → *žď (→ presumably ždž)
• *sj → *š
• *zj → *ž
• *lj → ľ /lʲ/
• *nj → ň /nʲ/
• *rj → ř /rʲ/

The combinations *gt and *kt merged into *ť in Proto-Slavic times and show outcomes identical to *ť in all languages. This combination occurred in a few lexical items (*dъťi "daughter" < *dъkti, *noťь "night" < *noktь), but also occurred in infinitives of verbs with stems ending in -g and -k, which would have originally ended in *-gti and *-kti. This accounts for the irregular infinitive ending some verbs such as Polish móc, Russian мочь from Proto-Slavic *moťi < *mog-ti, where normally these languages have infinitives in -ć and -ть respectively.

In the case of the palatal consonants that had resulted from the first regressive palatalization, the *j simply disappeared without altering the preceding consonant:

• *čj → *č [tʃ]
• *(d)žj → *(d)ž [ʒ]
• *šj → *š [ʃ]
• *ščj → *šč [ʃtʃ]
• *ždžj → *ždž [ʒdʒ]

In both East and South Slavic, labial consonants (*m, *b, *p, *v) were also affected by iotation, acquiring a lateral off-glide ľ /lʲ/:

• *mj → mľ
• *bj → bľ
• *pj → pľ
• *vj → vľ

Many researchers believe that this change actually occurred throughout Proto-Slavic and was later 'reversed' in West Slavic and in most dialects of the Eastern subgroup of South Slavic languages (Macedonian and Bulgarian, and the transitional Torlakian dialect) by analogy with related word forms lacking the lateral. The Codex Suprasliensis, for example, has земьꙗ < *zemja (i.e. an intrusive *ь where East and South Slavic languages have *ľ); compare:

• *zemja (→ *zemľa) → *zemьja →
  • Bulgarian: земя [zɛmˈja]
  • Macedonian: земја [ˈzɛmja]
  • Polish: ziemia [ˈʑɛ̃mʲja]
  • Torlakian: zemja [ˈzɛmja]

Some Northern Macedonian dialects, however, acquired an *n (e.g. [ˈzɛmɲa] < *zemja).

A few words with etymological initial *bj- and *pj- are reflected as *bľ- and *pľ- even in West Slavic:

• *pľьvàti "to spit" < PIE *(s)pieHu-, cf. Lithuanian spjáuti.
• *bľustì "to watch, to perk up" (1sg. *bľudǫ̀) < PIE *bʰeudʰ-.

Vowel fronting

Syllabic synharmony also worked in reverse, and caused the palatal articulation of a consonant to influence a following vowel, turning it from a back vowel into a front vowel. There were two sources for this process. The first was a preceding *j or a consonant that had undergone iotation. The second was the progressive palatalization (see below), which produced new palatal consonants before back vowels. The result of this fronting was as follows (with J acting as a cover symbol for any consonant with a palatal articulation):

• *Ja → *Je
• *Jā → *Jē
• *Ju → *Ji
• *Jū → *Jī
• *Jai → *Jei (→ *Jī)
• *Jau → *Jeu (→ *Jū)
• *Jų̄ → *Jį̄ (→ *Ję̇)

Towards the end of the Late Common Slavic period, an opposing change happened, in which long *Jē was backed to *Jā. This change is normally identified with the end of the tendency for syllabic synharmony.

Vowel fronting clearly preceded monophthongization, in that the outputs *Jei, *Jeu were later affected by monophthongization just as original *ei, *eu were. However, there is no guarantee that vowel fronting followed the progressive palatalization despite the fact that the output of the latter process was affected by vowel fronting. The reason is that the rule triggering vowel fronting may well have operated as a surface filter, i.e. a rule that remained part of the grammar for an extended period of time, operating automatically on any new palatal consonants as they were produced.

Vowel fronting did not operate on the low nasal vowel *ą (later *ǫ), cf. Old Church Slavonic znajǫ "I know". However, it did operate on the high nasal vowel *ų, leading to alternations, e.g. Old Church Slavonic accusative plural raby "slaves" (< *-ų̄) vs. koňę "horses" (< *-jį̄ < *-jų̄). See the section on nasalization for more discussion.

Prothesis

During the Common Slavic period, prothetic glides were inserted before words that began with vowels, consistent with the tendency for rising sonority within a syllable. *v was inserted before rounded vowels (*u, *ū), *j before unrounded vowels (*e, ē, *i, *ī). Not all vowels show equal treatment in this respect, however. High vowels generally have prothesis without exception in all Slavic languages, as do *e and *ē:

• *i- → *ji-
• *ī- → *jī-
• *u- → *wu- → *vu-
• *ū- → *wū- → *wȳ- → vȳ-
• *e- → *je-
• *ē- → *jē-

The development for *ji- and *jī- is somewhat uncertain. The glide *j may have retained allophonic status in that case, and is not found in many of the later Slavic languages.

Prothesis generally did not apply to short *a (which developed into *o or nasal *ǫ), although some East Slavic dialects seem to have developed it regardless. There seems to have been some uncertainty concerning the interpretation of long *ā as a rounded or unrounded vowel. Prothesis seems to have applied intermittently to it; when it does apply *ā- → *jā- is frequent, but *ā- → *vā- is also found.

Monophthongization and other vowel changes

*ū lost its labialization (possibly [ɯː] or [ɨː], represented hereafter as <y>, as in modern Polish), but not before prothesis occurred, as prothesis of *v before unrounded *y seems unlikely. This was closely followed by the monophthongization of diphthongs in all environments, in accordance with the law of open syllables. Following this change, short *a acquired non-distinctive rounding (probably [ɒ] in first instance), and is denoted as *o from this point onwards.

• *ū → *ȳ → y
• *au → *ū
• *eu → *(j)ū (the *j applied iotation to the preceding consonant, when possible)
• *ei → *ī
• *ai → *ē or ī^†
• *a → *o

^† In many common grammatical forms such as the nominative plural of o-stems (Schenker 2002:89), the second person imperative (Schenker 2002:103), in the second singular of athematic verbs and in the dative singular of the clitic personal pronouns, *ai became *ī (Schenker 2002:90).

Second regressive palatalization

Main article: Slavic second palatalization

Proto-Slavic had acquired front vowels, ē (possibly an open front vowel [æː]) and sometimes ī, from the earlier change of *ai to *ē/ī. This resulted in new sequences of velars followed by front vowels, where they did not occur before. Additionally, some new loanwords also had such sequences.

However, Proto-Slavic was still operating under the system of syllabic synharmony. Therefore, the language underwent the second regressive palatalization, in which velar consonants preceding the new (secondary) phonemes *ē and *ī, as well as *i and *e in new loanwords, were palatalized. As with the progressive palatalization, these became palatovelar. Soon after, palatovelar consonants from both the progressive palatalization and the second regressive palatalization became sibilants:

• ḱ → *c ([ts])
• ǵ → *dz → *z
• x́ → *ś → *s/*š

In noun declension, the second regressive palatalization originally figured in two important Slavic stem types: o-stems (masculine and neuter consonant-stems) and a-stems (feminine and masculine vowel-stems). This rule operated in the o-stem masculine paradigm in three places: before nominative plural and both singular and plural locative affixes.

		'wolf'	'horn'	'spirit'
Nominative	singular	*vьlkъ	*rogъ	*duxъ
	plural	*vьlci	*rozi	*duśi
Locative	singular	*vьlcě	*rozě	*duśě
	plural	*vьlcěxъ	*rozěxъ	*duśěxъ

Progressive palatalization

An additional palatalization of velar consonants occurred in Common Slavic times, formerly known as the third palatalization but now more commonly termed the progressive palatalization due to uncertainty over when exactly it occurred. Unlike the other two, it was triggered by a preceding vowel, in particular a preceding *i or *ī, with or without an intervening *n. Furthermore, it was probably disallowed before consonants and the high back vowels *y, *ъ. The outcomes are exactly the same as for the second regressive palatalization, i.e. alveolar rather than palatoalveolar affricates, including the East/West split in the outcome of palatalized *x:

• k → *c ([ts])
• g → *dz (→ *z in most dialects)
• x → *ś → *s/*š

Examples:

• *atiku(s) "father" (nom. sg.) → *aticu(s) → (with vowel fronting) Late Common Slavic *otьcь
• Proto-Germanic *kuningaz "king" → Early Common Slavic *kuningu(s) → Late Common Slavic *kъnędzь
• *vixu(s) "all" → *vьśь → *vьšь (West), *vьsь (East and South)

There is significant debate over when this palatalization took place and the exact contexts in which the change was phonologically regular. The traditional view is that this palatalization took place just after the second regressive palatalization (hence its traditional designation as the "third palatalization"), or alternatively that the two occurred essentially simultaneously. This is based on the similarity of the development to the second regressive palatalization and examples like *atike "father" (voc. sg.) → *otьče (not *otьce) that appear to show that the first regressive palatalization preceded the progressive palatalization.

A dissenting view places the progressive palatalization before one or both regressive palatalizations. This dates back to Pedersen (1905) and was continued more recently by Channon (1972) and Lunt (1981). Lunt's chronology places the progressive palatalization first of the three, in the process explaining both the occurrence of *otĭče and the identity of the outcomes of the progressive and second regressive palatalizations:

1. Progressive palatalization: *k > *ḱ (presumably a palatal stop) after *i(n) and *j
2. First regressive palatalization: *k/*ḱ > *č before front vowels
3. Fronting of back vowels after palatal consonants
4. Monophthongization of diphthongs
5. Second regressive palatalization: *k/*ḱ > *c before front vowels

(similarly for *g and possibly *x)

Significant complications to all theories are posed by the Old Novgorod dialect, known particularly since the 1950s, which has no application of the second regressive palatalization and only partial application of the progressive palatalization (to *k and sometimes *g, but not to *x).

More recent scholars have continued to argue in favor of the traditional chronology, and there is clearly still no consensus.

The three palatalizations must have taken place between the 2nd and 9th century AD. The earlier date is the earliest likely date for Slavic contact with Germanic tribes (such as the migrating Goths), because loanwords from Germanic (such as *kъnędzь "king" mentioned above) are affected by all three palatalizations. On the other hand, loan words in the early historic period (c. 9th century) are generally not affected by the palatalizations. For example, the name of the Varangians, from Old Norse Væringi, appears in Old East Slavic as варѧгъ varęgъ, with no evidence of the progressive palatalization (had it followed the full development as "king" did, the result would have been **varędzь instead). The progressive palatalization also affected vowel fronting; it created palatal consonants before back vowels, which were then fronted. This does not necessarily guarantee a certain ordering of the changes, however, as explained above in the vowel fronting section.

Accentual developments

See also: Proto-Slavic accent

Balto-Slavic

The Baltic languages, as well as conservative Slavic languages like Serbo-Croatian, have a complex accentual system with short and long vowels in all syllables, a free pitch accent that can fall on any syllable, and multiple types of pitch accent. (Vowel length is normally considered a separate topic from accent, but in the Slavic languages in particular, the two are closely related, and are usually treated together.) Not surprisingly, the historical development of accent in the Slavic languages is complex and was one of the last areas to be clearly understood. Even now, there is not complete consensus.

The Balto-Slavic languages inherited from PIE a free, mobile pitch accent:

1. 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).
2. The accent was free in that it could occur on any syllable, and was phonemic (i.e. its position could not be automatically predicted).
3. The accent was mobile in that its position could potentially vary among closely related words within a single paradigm.

An additional register distinction arose in Balto-Slavic times on certain types of syllables, between acute and circumflex. Eventually, this distinction was manifested as different types of pitch accent, with cognate words in Latvian, Old Prussian, Slovenian and Serbo-Croatian showing a distinction between rising ("acute") vs. falling ("circumflex") tones, with the terms based on the names of corresponding contour tones in Ancient Greek. (Note that Lithuanian also preserves the same tonal distinction, but has switched the nature of the tones, so that the Lithuanian acute is a falling accent while the Lithuanian circumflex is rising.) This distinction cannot be manifested on certain syllables containing a short vowel; rather it occurs on any of the following syllable types:

1. Those containing a long vowel.
2. Those containing a normal diphthong, e.g. *ai or *au.
3. Those containing a "sonorant diphthong", e.g. *ar *al *am *an not directly followed by a vowel.

In Proto-Balto-Slavic, however, the distinction between acute vs. circumflex could occur on all syllables (or at least, all syllables of the appropriate type), and is unlikely to have been a tonal distinction, but rather the presence of some feature (in acute syllables) vs. its absence (in circumflex syllables). This is based on various sound laws where the accent was drawn onto (or in some cases prevented from moving away from) acute syllables, but not circumflex syllables. The nature of the "acute" feature itself is unclear; it has variously been reconstructed as additional vowel length, the presence of a glottal stop, creaky voice, etc.

The acute feature is thought to stem largely either from PIE syllables containing a laryngeal consonant in the coda, or from vowels lengthened during Balto-Slavic times, e.g. through Winter's law. There is some dispute over whether all long vowels in early Balto-Slavic eventually developed an acute marking. The traditional theory holds this, suggesting that the acute vs. circumflex distinction was originally simply a length distinction in the nuclear vowel (hence, early on, all long vowels were acute, and only diphthongs could be distinguished as acute vs. circumflex). However, Frederik Kortlandt, and other researchers following him, maintain that the acute feature directly continues a PIE laryngeal, and that (e.g.) the PIE distinction between original *eh₁ and original long *ē is reflected as acute vs. circumflex, respectively. These researchers often refer to the acute feature as laryngealization.

Numerous changes ultimately led to a system in Proto-Slavic where only accented syllables contained an acute vs. circumflex distinction, and this was marked by pitch contours, i.e. rising (acute) vs. falling (circumflex). Frequently, the position and/or nature of the accent had changed due to numerous sound laws. At this time, this distinction could occur on the following syllable types:

• Those containing the long vowels *a *ě *i *u *y.
• Those containing the nasal vowels *ę *ǫ.
• Those containing a liquid diphthong.

Note that all of the above syllable types correspond to syllable types that could take register distinctions in late Balto-Slavic times (i.e. long vowels or diphthongs).

For more details, see Proto-Balto-Slavic.

Ivšić's law and the neoacute accent

See also: Ivšić's law

The most important accentual change in Common Slavic occurred near the end of the period. During the Late Common Slavic period, the short vowels *ĭ *ŭ (known as yers) developed into "strong" and "weak" variants according to Havlík's law. The weak variants could no longer carry an accent; as a result, if an accent had previously occurred on such a vowel, it was retracted onto the previous vowel (Ivšić's law), which gained a new type of rising accent, termed the neoacute. In the northern dialects (but not in Serbo-Croatian, Slovenian, or southern Slovakian dialects), short e and o gaining the neoacute were automatically lengthened. (This was one of many Common Slavic developments that disrupted the original distribution of short and long vowels and resulted in all vowels coming in both short and long variants.)

Example:

• Early Slavic *sȃndu(s) "court of law, trial" > Middle Common Slavic *sǫ̂dъ > MCS *sǫdъ̀ (by Dybo's law) > Late Common Slavic *sǫ̃dъ (= *sǫ́dъ) > Čakavian (Vrgara) sũd (G sg sūdȁ), Russian sud (G sg sudá).

The neoacute is often written with a tilde, as in LCS *sǫ̃dъ. The pronunciation is as a rising vowel, long if the vowel was originally long, short if the vowel was originally a short strong yer ь or ъ, and either long or short on original short e or o, depending on dialect (see above).

Retraction resulting in a neoacute accent also occurred in certain other morphological circumstances:

1. In the present tense of verbs in *-iti, e.g.:
   • MCS *nosì(tь) "he carries" > *nõsi(tь) > Russian но́сит nósit
2. From a vowel immediately preceded by an original *j:
   • PSl. *venzjè(ti) "he ties" > MCS *vęžè(tь) > LCS *vę̃že(tь) > Russian вя́жет v'ážet
   • MCS *voljà "will" > *vol'à > LCS *võl'a > Russian dial. vôlja

Common Slavic prosodic changes

Per Kortlandt (2011), the following prosodic changes happened in the Common Slavic period, following the period where quality and quantity were correlated. At this point, the former acute register in long syllables (resulting from Proto-Indo-European laryngeals and certain other developments) had been lost (becoming circumflex) except in all syllables that were either accented or directly following the accent. The acute had also been lost in stressed syllables in the mobile paradigm (class C) as a result of Meillet's law.

Note that some of these laws, e.g. Van Wijk's law, are controversial.

1. Development of tone: Stressed acute syllables, and all final open syllables, were pronounced with rising tone. Other stressed syllables were pronounced with falling tone.
2. Separation of quality and quantity, along with shortening of all pretonic vowels (vowels in syllables before the accent), which became short but maintained their quality. In general, later pretonic long syllables (as in class B) were accented at this time, becoming pretonic as a result of Dybo's law.
3. Loss of the acute register in immediately post-tonic syllables, along with vowel shortening. This led to a phonemic distinction in such syllables between short and long vowels with the same quality (the latter reflecting circumflex register). This is seen, for example, in the i stems, where short *-i in the dative singular is opposed to long *-ī in the genitive and locative singular. (Reflected later on as accentual differences in the root syllable, due to Stang's law.)
4. Van Wijk's law: Lengthening of vowels (except for yers and nasal vowels) following palatal consonants. This led to the increased occurrence of long vowels in the endings of jā and jo stems in class A, and corresponding differences in the position of the accent in class B. Some of these long vowels were later shortened by analogy, especially in endings that were unstressed in the mobile paradigm. (Note that this law is not accepted by all scholars.)
5. Contractions of vowels across /j/ in post-tonic syllables in some languages (especially Czech), producing a single long vowel. This only occurred when both vowels being contracted were unstressed, and did not occur at all in Russian.
6. Ivšić's law: Retraction of the accent from weak yers, leading to neoacute accent in the newly accented syllables.
7. Dybo's law: In non-mobile paradigms, non-acute syllables lost the accent to the following syllable. This created class B as distinct from class A. Formerly accented long syllables remained long, resulting pre-tonic length in class B. Newly stressed long vowels gained falling tone (which was then lost due to Stang's law, below).
8. Lengthening of short falling syllables (i.e. Balto-Slavic short syllables) in words that will be monosyllabic after loss of weak yers.
9. Loss of the acute register in stressed syllables, producing a short rising tone. (The acute register had already been lost elsewhere.)
10. Stang's law: Retraction of the stress from long falling syllables, producing neoacute accent. The syllables losing the stress became shortened. Most such syllables had retrieved the stress as a result of Dybo's law, and had many had become long due to Van Wijk's law (in jā and jo stems).
11. Analogical changes that smoothed out some of the complicated patterns produced by Stang's law. This in particular led to consistent neoacute root stress in jā stems, and neoacute root stress in the plural of jo stems.
12. Eventual loss of length in final syllables in most languages. However, the former long vowels are reflected to some extent in Slovene and Serbo-Croatian, and more directly by the neo-circumflex accent in Slovene, which developed early on from former acute-register syllables when followed by a long syllable or internal yer.

These developments are complex, but together they explain:

1. The difference between class A and class B, and the fact that class A reflects former acute register in the root. (Dybo's law produced class B accent.)
2. The occurrence of pre-tonic length in Serbo-Croatian in class B. (These syllables used to be stressed long syllables, before Dybo's law.)
3. The occurrence of length, or indication of former length (e.g. due to Slovene neo-circumflex accent), in the final syllables of class A jā and jo stems, but not the corresponding ā and o stems. (Due to Van Wijk's law.)
4. The occurrence of neoacute accent in certain class A jā stems. (These used to be class B, but the accent was retracted through a combination of Van Wijk's law and Stang's law.)
5. The occurrence of neoacute accent in the plural of certain class B jo stems, reflected especially in Russian. (Same basic explanation as previous.)
6. The pattern of retracted (neoacute) accent in class B, occurring sometimes when a weak yer used to follow (Ivšić's law) but also in certain other cases (Stang's law).

These can be seen in the various paradigms.

See also

• Proto-Slavic
• History of the Slavic languages
• Proto-Balto-Slavic
• Old Church Slavonic
• Slavic languages
• Balto-Slavic languages
• Proto-Slavic accent
• Slavic liquid metathesis and pleophony

References

In English

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In other languages

• Belić, Aleksandar (1921), "Најмлађа (Трећа) Промена Задњенепчаних Сугласника k, g и h у Прасловенском Језику", Јужнословенски Филолог (in Serbian), II: 18–39
• Bräuer, Herbert (1961), Slavische Sprachwissenschaft, I: Einleitung, Lautlehre (in German), Berlin: Walter de Gruyter & Co., pp. 69–71, 89–90, 99, 138–140
• Holzer, Georg (1995), "Die Einheitlichkeit des Slavischen um 600 n. Chr. und ihr Zerfall", Wiener Slavistisches Jahrbuch (in German), 41: 55–89
• Lehr-Spławiński, Tadeusz (1957), "Z dziejów języka prasłowiańskiego (Urywek z większej całości)", Езиковедски Изследвания В Чест На Академик Стефан Младенов (in Polish), Sofia
• Matasović, Ranko (2008), Poredbenopovijesna gramatika hrvatskoga jezika (in Croatian), Zagreb: Matica hrvatska, ISBN 978-953-150-840-7
• Mihaljević, Milan (2002), Slavenska poredbena gramatika, 1. dio, Uvod i fonologija (in Croatian), Zagreb: Školska knjiga, ISBN 953-0-30225-8
• Moszyński, Leszek (1984), "Wstęp do filologii słowiańskiej", PWN (in Polish), Warszawa
• Pedersen, H. (1905), "Die nasalprasentia und der slavische akzent", Zeitschrift fur vergleichende Sprachforschung (in German), 38: 297–421
• Vaillant, André (1950), Grammaire comparée des langues slaves, t.I: Phonétique (in French), Lyon—Paris: IAC, pp. 113–117
• Van Wijk, Nikolaas (1956), Les langues slaves: de l'unité à la pluralité, Janua linguarum, series minor (in French) (2nd ed.), 's-Gravenhage: Mouton