Hwanghae dialect is a dialect with the most elements of the Pyongan dialect among the Central dialects, and can also be divided into the other. Hwanghae dialect was commonly included among the Central dialects, but some researchers argue that it does not fit there comfortably. Because the division between South Korea and North Korea has prolonged, the Hwanghae dialect has been strongly influenced by the Pyongan dialect, and now more and more people see it as a sub-dialect of the Pyongan dialect, not the Central dialect. In any case, the central dialect can be said to be a dialect that can vary in various areas of the dialect depending on the criteria for the dialect compartment. For example, Hwanghae, Gyeonggi, Gangwon and Chungcheong are usually grouped together as the Central dialect region. But, many view that only Hwanghae, Gyeonggi, and Gangwon dialects are included in the central dialect, while Chungcheong dialect is considered as separate dialect. Gyeongsang (Southeastern) Spoken in Gyeongsang Province (Yeongnam) of South Korea, including the cities of Busan, Daegu and Ulsan. This dialect is easily distinguished from the Seoul dialect because its pitch is more varied. Six vowels, i, e, a, eo, o, u. Jeolla (Southwestern) Spoken in the Jeolla Province (Honam) region of South Korea, including the city of Gwangju. Ten vowels: i, e, ae, a, ü, ö, u, o, eu, eo.Jeju Spoken on Jeju Island off the southwest coast of South Korea and is sometimes considered a separate Koreanic language. The nine vowels of Middle Korean, including arae-a (ɔ). May have additional consonants as well. Several linguists have suggested that a further dialect area should be split from the Northeastern dialects: Ryukchin (Yukchin) Spoken in the historical Yukchin region which is located in the northern part of North Hamgyong Province, far removed from P'yŏng'an, but has more in common with P'yŏng'an dialects than with the surrounding Hamgyŏng dialects. Since it has been isolated from the major changes of Korean language, it has preserved distinct features of Middle Korean. It is the only known tonal Korean language. A recent statistical analysis of these dialects suggests that the hierarchical structure within these dialects are highly uncertain, meaning that there is no quantitative evidence to support a family-tree-like relationship among them. Some researchers classify the Korean dialects in Western and Eastern dialects. Compared with Middle Korean, the Western dialects have preserved long vowels, while the Eastern dialects have