The Lexical and Post-Lexical Phonology of Thai Tones*

Abstract

At first glance, the five-tone system of Thai looks quite simple. However, a detailed examination of the phonological distributions of segments and tones, combined with a careful analysis of the phonetic realizations of duration and pitch in both citation forms and connected speech, lead to the conclusion that the system is in fact complex and interesting. Based on data from an acoustic experiment, we claim that the tone bearing unit in Thai is the mora, and that previously unexplained restrictions on the distributions of tones in syllables closed by obstruents are the result of a relationship between the glottal feature and low tones. We describe and explain unexpected differences in the realization of tones in different phrasal positions in connected speech, and show that there are non-neutralizing contour tone simplifications that take place non-finally at the post-lexical level. Our analysis combines descriptive phonetics and phonology with both representational and constraint-based explanations (incorporating positional faithfulness and stratal Optimality Theory) to provide a unified account of the Thai tonal system. Our study supports a view of the grammar in which phonetics and phonology are separate, yet intricately related.