粵東閩方言有項特殊的音韻現象，就是m、n、ng 三組鼻音韻尾的合流。本文將以 筆者所調查的粵東閩方言調查的成果，對m、n、ng 這三個鼻音韻尾分合的地理分布， 進行語言、地理、年齡關係的交互研究。 經研究後發現，粵東閩方言的鼻音韻尾由內而外依次形成ng→m/ng→m/n/ng 的分 布，符合周圈論原則。並藉由 グロットグラム (glottogram) 的研究，發現單一ng 韻尾 與m、ng 二組尾韻的形式仍在向外擴展。 最後則對文獻上所見的此變化現象，與語言地圖上所見加以比較。我們認為此區鼻 音韻尾合流成m、ng 二組的時間，應該早在十六世紀就已出現，而非之前學者所認為的 十九世紀。

The merger of the nasal codas -m, -n, and -ng is a special phonological phenomenon of the Min dialect of Eastern Guangdong. Through the linguistic map, it is noted that we can find that Type 1 (only -ng coda) is found in the center, Type 3 (-m, -n, -ng codas) are distributed on the periphery, and Type 2 (-m and -ng codas) are in between, which fits perfectly with the theory of concentricity. By using glottograms, I show that Type 1 and Type 2 are expanding outward and that the merging of nasal codas forming Type 2 happened in the 16th century instead of in the 19th century, as previously indicated in the literature.