Middle Korean

The Korean language is attested from the early centuries of the Common Era in Chinese characters. The Featural writing system called hangul was introduced only in the fifteenth century.

The periodization of the historical stages of Korean is as follows:

Controversy remains over the proposed classification of Korean as Altaic languages. Korean being a language isolate, "Proto-Korean" is not a well-defined term, referring to the language spoken in prehistoric Korea during the Bronze and Iron ages. Other theories are the Dravido-Korean theory, or a connection to Austronesian.

Homer Hulbert claimed the Korean language was Ural-Altaic in his book, The History of Korea (1905). The classification of Korean as Altaic was introduced by Gustaf John Ramstedt (1928), but even within the Altaic hypothesis, the position of Korean relative to Japonic is unclear. A possible Korean–Japonic grouping within Altaic has been discussed by Samuel Martin, Roy Andrew Miller and Sergei Starostin. Others, notably Alexander Vovin, interpret the affinities between Korean and Japanese as an effect caused by geographic proximity sprachbund.

Old Korean (고대국어, 古代國語) corresponds to the Korean language from the beginning of the Three Kingdoms of Korea to the latter part of the North–South States Period, approximately from the first to the tenth century. Use of Classical Chinese by Koreans began in the fourth century or earlier, and phonological writing in Idu script was developed by the sixth century.

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