On Grammaticalization of "X_(yu)(于)" Structure

In modern Chinese,the members of Xyu(于) structure include not only typical words,such as verbs and adverbs,but also phrase-words which are between words and phrases.From the perspective of historical development,it experiences grammaticalization which include the decline of preposition yu(于),the development of bi-syllable word Xyu(于),the tendency of Xyu(于) further closer to the word and the disappearance of yu(于).Furthermore,Xyu(于) structure has some grammaticalization mechanisms and motivations,such as two-syllable word trend,semantic systems change,the prepositional phrases location moves and re-cognitive factors.