Slavic liquid metathesis and pleophony

Slavic liquid metathesis refers to the historical phenomenon of metathesis of liquid consonants occurring in the Common Slavic period in the South Slavic and West Slavic (specifically Czecho-Slovak) area. The closely related corresponding phenomenon of pleophony (also known as polnoglasie or full vocalization) occurred in parallel in the East Slavic languages. The change acted on syllables in which the Proto-Slavic liquid consonants *r and *l occurred in a coda position. The result of the change is dependent upon the phonological environment and accents, and varies among the Slavic languages; see below for details.

The change has been dated to the second half of the eighth century, before any Slavic languages were recorded in writing. Therefore, the change itself cannot be observed, but it can be inferred by comparing words in different Slavic languages. Evidence of the earlier state of affairs is also preserved in loanwords into and from early Slavic, as well as in cognates in other Indo-European languages, particularly in the Baltic branch.

During the Common Slavic period, a tendency known as the law of open syllables led to a series of changes that completely eliminated closed syllables. This was evident in Old Church Slavonic, which had no closed syllables at all: every syllable ended in a vowel. Some of these changes included the monophthongization of diphthongs, loss of word-final consonants (e.g. OCS nebo < PIE *nébʰos), simplification of some medial consonant clusters (e.g. OCS < *topnǫti etc.) and the formation of the nasal vowels *ǫ and *ę from *am/*an and *em/*en respectively.

The change discussed here is part of this process, and involved liquid consonants (grouped under the cover symbol R) *l or *r in a coda position, in environments which are traditionally designated as shown in table on the right. The application of the law of open syllables in such environments had different results in different Slavic dialects, and in fact presents some of the earliest evidence for differentiation into the multitude of Slavic languages. In some it manifested as the metathesis of a sequence of a liquid consonants followed by a vowel, whereas in others it manifested as an insertion of another vowel. In most cases, the effect was to eliminate the syllable-final consonants *l and *r so that the law of open syllables was maintained.

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