Structured Imbalances in the Emergence of the Korean Vowel System

ABSTRACT. This paper develops a structured account of the monophthongization and diphthongization processes which occurred in Korean during the 18th and the 19th centuries. These seemingly contradictory changes are seen as engendered by a persistent drive toward balance, symmetry and system optimization, with the result that Korean has come to abandon all off-glide diphthongs in favor of a rich set of (typologically less common) on-glide diphthongs. In 15th century Middle Korean, there were seven monophthongs (/i, , u, , o, a, /) as well as a number of both on-glide (/w, wa, yu, y, yo, ya, y/) and off-glide diphthongs (/y, uy, y, oy, ay, y/). As in the modern language, off-glides with /w / were not allowed (*/Vw/), and central unrounded / / went into combination only to form the off-glide diphthong /y/ (*/w/, */y/), which lasted into the 20th century before monophthongizing to /i / in most environments. By the end of the 18th century, the low rounded vowel / / had merged with /a/, and monophthongization ha