本研究以優選理論（Optimality theory, OT）分析梅縣客語的雙音節 變調。梅縣客語的雙音節變調，是由聲調內部的兩股力量所驅動－異 化（dissimilation）和同化（assimilation）。本研究提出與變調有關的聯 合制約（conjoined constraints），以解釋其聲調發生改變的特殊情況； 同時，為了在雙音節的文法中選出最佳的輸出值（outputs），一系列與 聲調特徵相關的信實制約（IDENT(F) constraints）也被納入分析之中。 最後，本研究也討論了梅縣客語中兩個不同的中平調（mid level tones）。

This paper presents an Optimality-Theoretic analysis of disyllabic tone sandhi in Meixian Hakka. In this paper, the alternations of tones are identified as being motivated by dissimilatory and assimilatory force at the tone internal structure. Since the tonal changes occur under highly marked condition, several locally conjoined constraints are posited to capture them. At the same time, a series of IDENT(F) constraints integrated with tone features are introduced into the analysis in order to explain the selection of the most optimal outputs in the di-tonal grammar. This study also discusses the existence of two phonologically distinct mid level tones in the dialect.