Korean has numerous small local dialects (called mal (말) [literally “speech”], saturi (사투리), or bang-eon (방언) in Korean). The standard language (pyojuneo or pyojunmal) of both South Korea and North Korea is based on the dialect of the area around Seoul, though the northern standard has been influenced by the dialect of P’yŏngyang. All dialects of Korean are similar to each other and at least partially mutually intelligible, though the dialect of Jeju Island is divergent enough to be sometimes classified as a separate language. One of the more salient differences between dialects is the use of tone: speakers of Seoul dialect make use of vowel length, whereas speakers of the Gyeongsang dialect maintain the pitch accent of Middle Korean. Some dialects are conservative, maintaining Middle Korean sounds (such as z, β, ə) which have been lost from the standard language, whereas others are highly innovative.
There is substantial evidence for a history of extensive dialect levelling, or even convergent evolution or intermixture of two or more originally distinct linguistic stocks, within the Korean language and its dialects. Many Korean dialects have basic vocabulary that is etymologically distinct from vocabulary of identical meaning in Standard Korean or other dialects, such as South Jeolla dialect /kur/ vs. Standard Korean 입 /ip/ “mouth” or Gyeongsang dialect /t͡ɕʌŋ.ɡu.d͡ʑi/ vs. Standard Korean /puːt͡ɕʰu/ “garlic chives”. This suggests that the Korean Peninsula may have at one time been much more linguistically diverse than it is at present. See also the Buyeo languages hypothesis.