Language & Information Society 14. This article focuses on two points. First, This article is concerned with investigating the usage of verb ``macho-`` in Middle Korean, also discussed syntactic and semantic properties of ``machoa`` and its lexicalization. I examined that actually verb ``macho-`` is realized with ``NP-i NP-eul NP-eul macho``, ``NP-i NP-eul NPe macho``, ``NP-i NP-eul NP-euro macho`` and it used with various meanings. In addition, I discussed that adverb ``machoa`` based on [verb ``macho-`` + conjoined endings ``-아``] is lexicalized. The word formation process for these(verb + conjoined endings ``-아``) is diachronic. but it is not productive. However, Adverb ``machoa`` underwent a process of extension in meaning. It now can modify verbs and be interpreted in ``just`` or ``by chance``. The meaning of ``just`` or ``by chance`` in adverb ``machoa`` was extended in the meaning of verb ``macho-``. As a result, ``machoa`` was listed as one of adverbs.