Ruki sound law

Ruki or iurk is the term for a sound law in the Satem group of Indo-European languages, especially Balto-Slavic and Indo-Iranian, describing context in which an original /s/ phoneme changes into /ʃ/:

:"s" > "ʃ" / "r, u, K, i _"

A sibilant "s" is retracted to a "Voiceless postalveolar fricative" after "i","u","r", or a velar (i.e. *k or *g which may have developed from earlier "k, g, gh"). Due to the character of the retraction, it was probably an apical sibilant (as in some dialects of Spanish), rather than the dorsal of English. The first phase ("s" > "š") seems to be universal; the later retroflexion (in Sanskrit and probably in Proto-Slavic as well) is due to levelling of the sibilant system, and so is the third phase - the retraction to velar "x" in Slavic and also in some Middle Indian languages, with parallels in languages like Spanish. This rule was first formulated for the Indo-European languages by Holger Pedersen, and it is known sometimes as the Pedersen law.

The name "ruki" comes from the sounds which cause the phonetic change. It associates with a Russian word which means 'hands' or 'arms'.

Applications to language groups

The rule was originally formulated for Sanskrit. It was later proposed to be valid in some degree for all Satem languages, and exceptionless for Indo-Iranian languages. In Baltic and Albanian it is more or less limited or affected by other sound laws. Nevertheless, it has to have been universal in these branches of the IE languages, and the lack of e.g. Slavic reflexes before consonants is rather due to merger of these with the reflexes of other sibilants.

Exceptions in Slavic languages

In Slavic languages the process is regular before a vowel, but it does not take place before consonants. The final result is the voiceless velar fricative "x", which is even more retracted than the "š". This velar fricative changed back into "š" before a front vowel or the voiced palatal approximant "j".

Exceptions in Indo-Iranian languages

In Indo-Iranian *"r" and *"l" merged, and the change worked even after the new sound. This has cited as evidence by many scholars for an argument for the later influence of Iranian languages on Proto-Slavic. There are obvious drawbacks in the theory - the two sounds must have been very close ("r"/"l"), so that both could have triggered the change in Indo-Iranian, and what's more, there are no real examples of this change working in Slavic, and it is also doubtful, that only this change (ruki) and no other such change of sibilants (e.g. "s" > "h") was borrowed into Slavic.