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.
Comparison of Japanese and Korean
The geographically close Japanese and Korean languages share considerable similarity in typological features of their syntax and morphology while having a small number of lexical resemblances and different native scripts (although they both use the Chinese characters, called hanja in Korea and kanji in Japan; see "Writing" section). Observing the said similarities and probable history of Korean migration to prehistoric Japan, linguists have formulated different theories proposing a genetic relationship between them, though these studies either lack conclusive evidence or were subsets of theories that have suffered large discredit (like versions of the well-known Altaic hypothesis that mainly attempted to group the Turkic, Mongolian and Tungusic languages together). Due to the lack of a sufficient reconstruction of Proto-Japonic and Proto-Korean, any relation between the languages that may have existed may never be conclusively proven (see: Japonic migration from Korea hypothesis and Gaya language).