Hanja
Although a phonetic Korean alphabet, now known as Chosŏn'gŭl or Hangul, had been created by Sejong the Great, it did not come into widespread official use until the late 19th and early 20th century. Thus, until that time it was necessary to be fluent in reading and writing Hanja in order to be literate in Korean, as the vast majority of Korean literature and most other Korean documents were written in Literary Chinese, using Hanja as its primary script. Today, a good working knowledge of Chinese characters is still important for anyone who wishes to study older texts (up to about the 1990s), or anyone who wishes to read scholarly texts in the humanities. Learning a certain number of Hanja is very helpful for understanding the etymology of Sino-Korean words, and for enlarging one's Korean vocabulary. Today, Hanja are not used to write native Korean words, which are always rendered in Hangul, and even words of Chinese origin—"Hanja-eo" ()—are written with the Hangul alphabet most of the time, with the corresponding Chinese character often written next to it in order to prevent confusion with other characters or words with the same phonetics.
Korean language
Modern Korean descends from Middle Korean, which in turn descends from Old Korean, which descends from the language spoken in Prehistoric Korea (labeled Proto-Korean), whose nature is debated, in part because Korean genetic origins are controversial (See Koreans for archaeological and genetic studies of the Koreans). A relation of Korean (together with its extinct relatives which form the Koreanic family) with Japanese (along with its extinct relatives which form the Japonic family), has been proposed by linguists such as William George Aston and Samuel Martin. Roy Andrew Miller and others suggested or supported the inclusion of Koreanic and Japonic languages (because of a certain resemblance) in the purported Altaic family (a macro-family that would comprise Tungusic, Mongolian and Turkic families). The Altaic hypothesis has since been largely rejected by most linguistic specialists.
Chinese characters arrived in Korea (See Sino-Xenic pronunciations for further information) together with Buddhism during the Proto-Three Kingdoms era in the 1st century BC. It was adapted for Korean and became known as Hanja, and remained as the main script for writing Korean through over a millennium alongside various phonetic scripts that were later invented such as Idu, Gugyeol and Hyangchal. Mainly privileged elites were educated to read and write in Hanja. However, most of the population was illiterate. In the 15th century, King Sejong the Great personally developed an alphabetic featural writing system known today as Hangul. He felt that Hanja was inadequate to write Korean and that this was the cause of its very restricted use; Hangul was designed to either aid in reading Hanja or replace Hanja entirely. Introduced in the document ""Hunminjeongeum"", it was called ""eonmun"" (colloquial script) and quickly spread nationwide to increase literacy in Korea. Hangul was widely used by all the Korean classes but often treated as ""amkeul"" (script for female) and disregarded by privileged elites, whereas Hanja was regarded as ""jinseo"" (true text). Consequently, official documents were always written in Hanja during the Joseon era. Since most people couldn't understand Hanja, Korean kings sometimes released public notices entirely written in Hangul as early as the 16th century for all Korean classes, including uneducated peasants and slaves. By the 17th century, Korean elites Yangban and their slaves exchanged Hangul letters; that indicates high literacy rate of Hangul in Joseon era. Today, Hanja is largely unused in everyday life due to its inconvenience, but it is still important for historical and linguistic studies. Neither South Korea or North Korea opposes the learning of Hanja, though they are not officially used in North Korea anymore, and their usage in South Korea is mainly reserved for specific circumstances, such as newspapers, scholarly papers, and disambiguation.