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The purpose was research; 1) to study lexical categories of Mon language spoken in Mon State, 2) to analyze word-formation of Mon language spoken in Mon State. This research is quantitative and documentary. The researcher the study was based on the comparative study of Mon morphology from the modern usage Mon, English, books, Mon Dictionary, article, online research. The population used in this research was Mon people born at Thanbyuzayut in Mon state consisting of 5 persons. The area of research is Mon people at Thanbyuzayut in Shan state union of Myanmar. Research method, the tool used in the study, the researcher makes interview and document research. The research studied from informants' native speakers for five persons—an area of research Thanbyuzayut in the Mon state of Myanmar. Research method, the tool used in the research was an interview and document research. The researcher studied from informants' native speakers for five persons.  The documentary Mon dialect data had been used for interviewing by way of quantitative methods linguistics.

             The results of the research:

There were simple forms, and compound forms of they can be classified into based on Mon language. The morpheme refers to the study of monomorphemic and polymorphemic forms such as composite forms, prefix-derived forms, suffix-derived forms, reduplicated forms, and rhyming forms. The compound word of Mon is divided into four main types; nominalization compound, class term compound, word-class compound, and semantic compound.

             The word classes of Mon as a part of speech are nouns, pronouns, adjectives, numerals, verbs, adverbs, prepositions, conjunction, interjection, and final particles.