Korean classification is often debated. Many Korean and Western linguists recognize a kinship to the Altaic languages. However, this is not well demonstrated, and many consider Korean a language isolate. Others believe that Japanese and Korean may be related; still others believe this is not so, and any similarities are simply due to a sprachbund effect – see here for morphological features shared among languages of the East Asian sprachbund.
The Korean relationship with Altaic and proto-Altaic has been much argued as of late. Korean is similar to Altaic languages in that they both have the absence of certain grammatical elements, including number, gender, articles, fusional morphology, voice, and relative pronouns (Kim Namkil). Korean especially bears some morphological resemblance to some languages of the Eastern Turkic group, namely Sakha (Yakut).
Korean has several dialects (called mal [literally speech], bang-eon, or saturi in Korean). The standard language (pyojuneo or pyojunmal) of South Korea is based on the dialect of the area around Seoul, and the standard for North Korea is based on the dialect spoken around P'yongyang. These dialects are similar, and in fact all dialects except that of Jeju Island are largely mutually intelligible. The dialect spoken there is classified as a different language by some Korean linguists. One of the most notable differences between dialects is the use of stress: speakers of Seoul Dialect use stress very little, and standard South Korean has a very flat intonation; on the other hand, speakers of Gyeongsang Dialect have a very pronounced intonation that, to Western ears, often sounds European.