Abstract

Abstract According to the investigation of 12,096 given words in the eight different Tibetan dialects, the process of vowel assimilation has continued throughout the development of the Tibetan language. The purpose of this study is to carefully examine all the data and give a preliminary analysis of the processes of vowel assimilation in the Tibetan language based on a comparison of ancient and modern Tibetan dialects. The results of the study indicate: ( 1 ) The vowel assimilation in the development of ancient Tibetan to modern Tibetan represents at least two different major types. One is conditioned by the vowel of the final syllable, the other is triggered by the vowel of the first syllable. Since Tibetan words most frequently maintain only two syllables, the conditioning effect of the vowel in one syllable is therefore understood as the effect on the immediate neighboring syllable. (2) Depending on the direction of the assimilation, these two types of assimilation can be further distinguished as raising, lowering, fronting, fronting-lowering, back-lowering and back-raising assimilations as subtypes. All of these types and subtypes can be formulated in general. There are no backing and fronting-raising assimilations found in the investigative pool. (3) Modern Tibetan dialects which commonly retained both old and new forms throughout the development should be considered for examining the orders of the assimilatory process. It is clear that the orders depend on the direction of the assimilation. Assimilatory processes such as raising and lowering represent orders of change in vowel height. In the fronting assimilation, the order of fronting is direct. There is no intermediate stages between the [+front] and [+back] vowels. In the fronting-lowering assimilation, fronting acts first; lowering occurs second. In backing-raising assimilation, the assimilatory order is: raising acts first, backing occurs after raising. Since vowels in both the first and final syllables of a Tibetan word are commonly quite stable, and not liable to be lost in development, the triggering environment therefore remains stable. As a consequence, the types and orders of assimilatory processes in the development of ancient Tibetan to modern Tibetan present vowel harmony in nature.