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 mixed script
Korean mixed script, known in Korean as "hanja honyong" (), "Hanja-seokkeosseugi" (漢字섞어쓰기, 한자섞어쓰기), 'Chinese character mixed usage,' or "gukhanmun honyong" (), 'national Sino-Korean mixed usage,' is a form of writing the Korean language that uses a mixture of the Korean alphabet or "hangul" () and "hanja" (, ), the Korean name for Chinese characters. The distribution on how to write words usually follows that all native Korean words, including grammatical endings, particles and honorific markers are generally written in "hangul" and never in "hanja". Sino-Korean vocabulary or "hanja-eo" (), either words borrowed from Chinese or created from Sino-Korean roots, were generally always written in "hanja" although very rare or complex characters were often substituted with "hangul". Although the Korean alphabet was introduced and taught to people beginning in 1446, most literature until the early twentieth century was written in literary Chinese known as "hanmun" ().