Study of the potential word of "De" in Chinese textbooks of the Korean era

Chinese textbooks in the era of the Korean reflect the evolution of from Yuan Dynasty to the last stage of Qing Dynasty.De has gone through the course of grammaticalization: from transitive verb to auxiliary verb and then to semi-free verb,until finally becomes the auxiliary word which expresses potential completely.In addition,the data also show that,the structure of V De/No De was used frequently during the Yuan and Qing Dynasties,yet,the rate of utilization of it gradually declined in the early of the Qing Dynasty.Meanwhile,the other structure of V De/ No C and some helper verbs have been developed gradually in the competition of it since the early Qing Dynasty.The reason of the diachronic grammar evolution in northern dialect is determined by the restriction and influence of the language's social attributes.