On Bactrian umlaut

The aim of this paper is to explore the phonetically grounded diachronic phonological change known as ‘umlaut’ in Bactrian. In particular, this regards the fronting (palatalizing) in Bactrian of a to and of ā to before high front vowels, as well as the backing and rounding of a to before u. Studies devoted to Bactrian phonology mention the i-umlaut, labelled as palatalization, but disregard the u-umlaut. In the recent studies on Bactrian grammar (in a wider sense), both phenomena are described: the i-umlaut as palatalization and the u-umlaut as sporadic vowel assimilation. What has not yet been noted is that while cases where the front vowels arise are context free (i.e., without conditioning environments), the backing and rounding of a to before u is context-sensitive since it occurs only in a labial environment: we can compare, for example, Bactrian μολο “wine” < Proto-Iranian *madu-, with Bactrian κασοκο “little” < *kasu-ka-, Avestan kasu-. The present study thus re-examines Bactrian umlaut and offers a systematic description of this sound change in different positions.