Abstract: The irregular phenomena of pronunciation are important windows to observe the evolution of language, hence explaining these phenomena is a significant way to understand the history of language and to summarize the law of language evolution. As for the Mugedao dialect of Hmong spoken in parts of Sichuan, Yunnan and Guizhou, the numeral “ten” has many syllable forms with similar sounds. But in composing the numeral, the pragmatic distribution is complementary, and the competition fact appears in the spoken language. Combining with other reasonable methods of linguistic study, this paper observes these phenomena and illustrates the gradual change of the diffusion of some linguistic facts in language through applying the method of historical linguistics.

Key words: language competition, lexical diffusion, spilt and merge