The term“apical vowel” is first seen in Bernhard Karlgren’s work Études sur la phonologie chinoise and widely accepted by Chinese linguists. However apical vowel is merely an articulatory description. In phonological analyses apical vowels actually create problems. They cannot be described as front, central, or back, and even cannot be included in a regular vowel chart. In this article we examine the historical process which produced the apical vowels and related changes before and after the Menggu Ziyun 蒙古字韻. Based on the analyses it is quite obvious that apicalization and other related changes after the retroflex initials are the results of the same phonological change. The result of this change is simply to delete the [+front] feature of the final after the retroflex initials. Thus phonologically the so-called apical vowels have to be central vowels that lack the front feature. The nature of this change can also be learned from analysis of the hP’ags-pa spellings employed in the MGZY. The hP’ags-pa spellings of the Yuan time not only provide the first phonetic transcription of a Chinese phonology; they also provide an insightful phonological analysis.
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