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
The hypothesis that Korean might be related to Japanese has had some supporters due to some overlap in vocabulary and similar grammatical features that have been elaborated upon by such researchers as Samuel E. Martin and Roy Andrew Miller. Sergei Anatolyevich Starostin (1991) found about 25% of potential cognates in the Japanese–Korean 100-word Swadesh list. Some linguists concerned with the issue, for example Alexander Vovin, have argued that the indicated similarities between Japanese and Korean are not due to any genetic relationship, but rather to a "sprachbund" effect and heavy borrowing, especially from ancient Korean into Western Old Japanese. A good example might be Middle Korean "sàm" and Japanese "asá", meaning "hemp". This word seems to be a cognate, but although it is well attested in Western Old Japanese and Northern Ryukyuan languages, in Eastern Old Japanese it only occurs in compounds, and it is only present in three dialects of the Southern Ryukyuan language group. Also, the doublet "wo" meaning "hemp" is attested in Western Old Japanese and Southern Ryukyuan languages. It is thus plausible to assume a borrowed term. (See Classification of the Japonic languages for further details on a possible relationship.)