Words which in southern Greek dialects contain [azis], [úsis], and other sequences of stressed vowel + sibilant + [i] + sibilant, appear widely in the north with [áys], [úys] etc., and the phenomenon constitutes a major crux in modern Greek phonology. Although the problem has been widely discussed, no really satisfactory solution based on attested processes has been offered. It is the purpose of this paper to review the data, criticize existing treatments, and offer a new proposal.

There are in principle infinitely many descriptions to fit the data of language, whether synchronic or diachronic. Although in practice one is seldom confronted with more than a few alternatives within any one descriptive system, the difficulty of choosing between these alternatives in a principled way has been well recognized since Chao. Two sorts of criteria have traditionally been and continue to be invoked more or less explicitly, criteria which may be subsumed under the headings of simplicity and naturalness. Historical linguists have long had to cope with certain sets of data for which neither type of criterion could dictate unique solutions. There is now a growing list of similar dilemmas in generative descriptions. The present paper presents a case where non-unique generative and reconstructional accounts