In this study, we try to describe on the characteristic on the Korean standard language selection through the knowledge of history of korean phonology and dialects. According to current Korean standard language regulation, ‘ttwari(똬 리), mu(무)’ is singular Korean standard language, but ‘noeul(노을)/nol (놀)’ is plural Korean standard language. ‘*ttoari(또아리), *muu(무우)` is in general use in korean, ‘ttwari(똬리), mu(무), ‘noeul(노을)/nol(놀)’ are diachronically related to Word-medial consonants ‘β(ㅸ), z(ㅿ)’. therefore ‘ttwari(똬리), mu(무), ‘noeul(노을)/nol(놀)’ is ought to make not singular Korean standard language but plural Korean standard language.