The purpose of this study is to explore vowel mutation of Daejeon dialect as one of subordinate dialects of Korea's central area dialects. It is well known that vowel mutation is realized showing both active and various aspect in any local area. In that context, Daejeon dialect is no exception. In specific, among various vowel mutations, diphthongization of monophthong and monophthongization of diphthong will be focused on with their characteristics identified. They might be opposed phenomena; however, they were realized complicatedly in Daejeon dialect. Regarding vowel system, detailed research questions were provided to figure out status and identification of Daejeon dialect: how their phonological feature were realized and how they were related with neighboring area.
The results of this study were summarized as followings:
First, vowel system of Daejeon dialect was not quite different from that of central dialect; however, (wɨ) exists in Daejeon dialect as well as raising diphthong (yɨ).
Second, a variety of monophthongization of diphthong in Daejeon dialect were observed. Major mechanism of these monophthongizations were reflection of deletion of semi-vowel and diachronic change of ‘여(yƏ)’. For instance, the realization of connective ending ‘-(으)며(myƏ)’ to ‘-(으)메(me)’ was a result of the reflection of ‘여(yƏ)→에(e)’ within lexical morpheme. That was active to be realized as ‘여(yƏ)→에(e)’( as in 메누리(menuri)(며느리(myƏnɨri)), 베(pe)(벼(pyƏ)) etc.) under the condition of bilabial, which could be also found in the central dialects. Unlike South west dialect, Daejeon dialect was active in realization of ‘-(으)문(mun)’ and ‘-(으)무는(munɨn)’ respectively after getting through vowel raising (‘-머(mƏ)→-므(mɨ’) and labialization (‘-므(mɨ)→-무(mu)’); South west dialect stays on the procedure of semi vowel deletion as in -(으)면(myƏn)→‘-(으)먼(mƏn), -(으)면은→(myƏnɨn)(‘-(으)머는(mƏnɨn)’. Therefore, this study provided the transfer procedure of ‘-면(myƏn)→-먼(mƏn)(deletion of semi vowel)→-믄(mɨ)(vowel raising)→-문(mun)(labiolization)’.
Third, monophthongization of ‘의(ɨy)’ found in Daejeon dialect was well featured in possessive particle. When the final word was consonant of the preceeding substanstive, 의(ɨy) was realized as ‘-에’ and also as ‘으(ɨ)~우(u)’ in the case of biolabial.
Fourth, a variety of diphthongizations of monophthong were observed in Daejeon dialect. In addition to ‘애(Ɛ)→야(ya)’(as in 뱜:(pyam)(뱀:(pƐm)), 샴:(syam)(샘:(sƐm)) etc.) within lexical morpheme, termination endings of ‘-대(tƐ), -ㄴ대(ntƐ), -는대(nɨntƐ)’ were realized as ‘-댜:(tya), -ㄴ댜:(ntya), -는댜:(nɨntya) respectively’; ‘애(Ɛ)+어(Ə)’ structure was realized as ‘야:’ as well as ‘해(hƐ)+어(Ə)→햐:(hya), 패(phƐ)+어(Ə)→퍄:(phya), 때(t,Ɛ)+어(Ə)→땨:(t,ya)’ and ‘되(tö)+어(Ə)’→ ‘댜:(tya)’. Also, typical way of speaking in Chungnam dialect was observed by dragging ending as found where ‘애(Ɛ)→야:(ya)’ was realized in ‘그래(kɨrƐ)→그랴(kɨrya)’.
Fifth, one of the main vowel mutations in Daejeon dialect was realization of interrogative ‘어(Ə)X’ into ‘워(wƏ)X’; this vowel mutation, added with semi vowel 'w', was typical phenomenon of Chungnam dialect, however, Daejeon dialect showed abnormal realization of ‘(wɨ)’ by vowel raising from ‘워(wƏ)’ to ‘어(Ə)→으(ɨ)’ selectively.
According to previous studies (Do, S. H. 1977 & Kim, J. T. 2010:426-467), Daejeon dialect showed similar linguistic feature of Jeolla province in its phonology, grammar, and lexicon as it neighbored upon local area in north Jeolla province such as 'Seocheon, Buyeo, Nonsan, and Guemsan'. However, this study provided a variety of vowel mutations which showed similarity with Chungnam dialect rather than Jeonbuk dialect.