Grammaticalization of the Verb "Xu (须)"

As a Verb in ancient Chinese,Xu(须) has been through the process of grammaticalization: auxiliary-adverb-conjunction,when syntactic,semantic and pragmatic factors have all played important roles.The main evolution mechanism that turned the verb Xu(须) into the auxiliary verb Xu(须) is expansion,appeared as the complication of syntactic and the subcategory variation of the noun and verbs.The reason that causes the next grammaticalization is semantic presupposition and abduction inference.In terms of semantic pattern,the development of Xu(须) is along the way of deontic modality-epistemic modality.