Korean dialects
A number of Korean dialects are spoken in the Korean Peninsula. The peninsula is extremely mountainous and each dialect's "territory" corresponds closely to the natural boundaries between different geographical regions of Korea. Most of the dialects are named for one of the traditional Eight Provinces of Korea. One is sufficiently distinct from the others to be considered a separate language, the Jeju language.
The standard language
In South Korea, Standard Korean (표준어/標準語) is defined by the National Institute of the Korean Language as "the modern speech of Seoul widely used by the well-cultivated" (교양있는 사람들이 두루 쓰는 현대 서울말). In practice, it tends not to include features that are found exclusively in Seoul.
In North Korea, the adopting proclamation stated that the Pyongan dialect spoken in the capital of Pyongyang and its surroundings should be the basis for the North Korean standard language (Munhwaŏ); however, in practice, it remains "firmly rooted" in the Seoul dialect, which had been the national standard for centuries.