This paper is a study about the origination and application conditions of Umlaut. It's concreted on Jeonnam dialect umlaut cases. Follows are conclusions as application conditions;(1) Triggers of umlaut are palatal consonant /č/, /čʰ/, /č'/ and alveolus sound /s/, /s'/, /l/, /n/, /t/, /t'/, /tʰ/ and target is /ɨ/, the end product sound is /i/.
Triggers are [+coronal] feature, target is [+dorsal]feature and the result also is [+coronal] feature. It means that umlaut is assimilation what [+coronal] feature makes [+dorsal] feature become [+coronal] feature.
(2) The frist conditon is priority of environment, an umlaut comes after /s/, /s'/. But it has product many cases after /č/, /čʰ/, /č'/ from the late 19C until now. This phenomenon happens because /č/, /čʰ/, /č'/ was still not completed as palatal consonant from a dental sound. Umlaut has application priority when trigger and target are close each other.
And if trigger has same articulation, umlaut is applied by short distance between trigger and target. This condition comes frist than another application conditions.
When fricative consonant /s/, /s'/ and affricate consonant /č/, /čʰ/, /č'/ are same articulation as a dental sound, it apply on /ɨ/ which is closest vowel after them and closest fricative consonant. But if /č/, /čʰ/, /č'/ are palatal consonant, this case are more productive because they are closer with following vowels.
(3) Umlaut is applied frequently closer between articulation and following vowel /ɨ/. For example, if classify alveolus sounds by distance then gets this result - /s/, /s'/ > /l/ > /n/, /t/, /t'/, /tʰ/. Therefore the farthest /s/, /s'/ is the most productive and the closest /n/, /t/, /t'/, /tʰ/ is unproductive.
(4) Umlaut has application priority when related morphologically. This condition extend its application range widely to the conjugation and declenstion in the morpheme.
It has two more conditions- word formation and language form. In the word formation, umlaut apply from simple word to compound word, and in language form, it extend from original Korean to Sino-Korean.