In order to understand the characteristics of a middle construction and explain its formation, we should inspect the lexical stucture, the syntactic structure and the logical form of it synthetically. A middle construction is derived by the diathesis alternation that causes the object of a transitive verb to realize as the subject of syntactic structure. This change implies the cognitive process from the description of an individual event to the statement of a general state. A middle construction has two argument. The one is the understood but unexpressed implicit argument which has generic agent θ-role at the lexical category. The other is the explicit argument of subject at the syntactic structure which was the object with theme/patient. or with affected θ-role at the lexical structure. The middle verb of activity or accomplishment doesn`t describe a specific event but a noneventive state. A transitive verb changes into a middle verb which incorporates with the abstract morpheme. of an aspectual delimitedness feature in course of undergoing a `change of state` in the syntactic derivation. If a transitive verb becomes a middle verb, it should select the argument with theme or patient θ-role as its new subject suppressing old one. Accordingly a middle verb usually combines with a manner adverbial or prototypical tense aspect. The formation of a middle construction can be explained principlely through the morphological checking theory that attracts the formal feature of lexical items to the functional category at the syntactic structure or at the level of logical form.

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