Abstract: In Old Chinese,there are three special structures in which “Wu” is used:“Wu” + verb;“Wu” + adj.to form “Wujing”,“Wuyi” and “Wuying”;the fixed disyllabic functional words “Wunai”,“Wuyi” and “Wuning”.There is no common explanation of the “Wu” in these three structures,and no discussion on their relationships from the perspective of semantic evolution or grammaticalization.This paper reviews the three usages of “Wu” mentioned above,and discovers the grammaticalized process of “Wu”.In the first structure,“Wu”,as a frequency adverb,means frequently.In the second structure,“Wu”,as a morpheme,indicates the continuous increase of amount or extension of a state.In the third structure,“Wu”,as a morpheme,expresses the tone of speculation and judgement based on the repeated historical experience and natural laws.This paper links the three usages of the “Wu” above with its etymological meaning,explores the different stages of “Wu” from the free word with concrete meanings to the morpheme in fixed disyllabic functional words,and finds that the grammaticalization took place step by step.

Key words: grammaticalization, Mei, Wu, Wunai, Wuyi, Wuning