오늘날 대부분의 경상도 하위 방언에서는 /ㅔ/ 와 /ㅐ/가 합류되어 /E/로, /ㅡ/와 /ㅓ/가 합류되어 /ヨ/로 실현된다. 그런데, 이달이 합류되는 통시적 과정을 살펴보면 이틀의 합류는 동기적 측면에서 인과적으로 관련 되어 있음을 발견하게 된다. 그 관련성은 다음과 같다.
경상도 방언에서 15, 16세기 모음 체계는 전설평순모음에 /ㅣ/, 증설평순모음에 /ㅡ/, /ㅓ/, /ㆍ/, /ㅏ/, 후설원순모음에 /ㅜ/, /ㅗ/가 각각 자리 잡고 있어서 체계적으로 불균형을 이루었다. 이러한 불균형을 해소하기 위해 17세기 무렵에 전설고모음 /ㅣ/의 음역 아래에 있는 빈칸에 /e/, /ε/가 생성된다. 그 결과, 전설모음 쪽으로 상당히 치우쳐 있던 /ㅓ/가 안전 영역을 찾아 /ㅡ/의 음역 아래로 이동한다. 그렇지만, /ㅓ/는 /ㅡ/에 지나치게 가까운 음역에 놓임으로써 /ㅡ/와 합류하게 되며, 19세기 무렵에는 이들의 합류음 /ヨ/가 생성을 완료하게 된다. /ヨ/의 생성은 중설모음을 4서열 체계에서 2서열 체계로 조정하는 결과를 낳게 되며, 또한 이미 2서열 체계를 유지하고 있는 후설모음과 체계적으로 균형을 이루게 되는 결과도 낳게 된다. 한편, 2서열 체계로 균형을 이루고 있는 중설모음과 후설모음은 3서열 체계로 남아있던 전설모음에 압력을 가하여 모음 체계의 전체적인 안정성을 도모하게 된다. 그 결과, 음성적으로 유사한 /e/와 /ε/가 20세기 초에 /E/로 합류한다.
In Gyeongsang-do Dialect of Korean, it has been assumed that the merger of /ㅔ/ with /ㅐ/ results in /E/, and the one of /-/ with /ㅓ/ results in /ヨ/. When we scrutinize the diachronic process of the mergers, we can find out that these two mergers are causally related to each other in their development. We can summarize their relationship as follows;
creation of /e/, /ε/(17C) ⇒ move of /ㅓ/(17, 18C) ⇒ creation of /ヨ/(17C: lag phase)(18C; log phase)(19C: equilibrium) ⇒ creation of /E/(18C: lag phase)(19C: log phase)(20C:equilibrium)
In Gyeongsang-do Dialect of Korean, the vowel system in 15th & 16th centuries was very unbalanced, since it had retained /ㅣ/ as a front vowel, /ㅡ/, /ㅓ/, /ㆍ/, /ㅏ/ as central vowels, and /ㅜ/, /ㅗ/ as back vowels. To settle this disparity, /e/ and /ε/ were created in 'the case vide' below the region of articulation of /ㅣ/ as a high front unrounded vowel. As a result of the creation, to secure phonetic distance between phonemes, /ㅓ/, which had been slanted toward the direction of front vowels, moved to the lower part of the region of articulation of /ㅡ/. Nevertheless, /ㅓ/ could not secure 'a safe distance' (F. 'marge de securite'), and it triggered the movement of the vowel into the region extremely near to /ㅡ/. As a result, /ㅓ/ merged with /ㅡ/, and their merger, /ヨ/, was completed around the 19th century. The creation of /ヨ/ resulted in the mediation of the central vowels from the 4-layered order system to a 2-layered order system, which influenced them to keep balance with the back vowels systematically. And further, the central vowels and back vowels that keep their balance through their 2-layered order system, put pressure on the front vowels, which had maintained a 3-layered order system. This resulted in promotion of an overall systemic stability. Consequently, /e/ and /ε/, which were similar phonetically, were merged into /E/ in the early 20th century.
This study is different from past works, in the respect that they have not dealt with the diachronic relatedness between /E/ and /ヨ/ and have had the creation of /ヨ/ explained by the hypothesis of the backing of /ㅓ/, resulting from the loss of /ㆍ/.