Korean is the native language for about 80 million people, mostly of Korean descent. It is the official and national language of both North Korea and South Korea (geographically Korea), but over the past 75 years of political division, the two Koreas have developed some noticeable vocabulary differences. Beyond Korea, the language is recognized as a minority language in parts of China, namely Jilin Province, and specifically Yanbian Prefecture and Changbai County. It is also spoken by Sakhalin Koreans in parts of Sakhalin, the Russian island just north of Japan, and by the Koryo-saram in parts of Central Asia. The language has a few extinct relatives which—along with the Jeju language (Jejuan) of Jeju Island and Korean itself—form the compact Koreanic language family. Even so, Jejuan and Korean are not mutually intelligible with each other. The linguistic homeland of Korean is suggested to be somewhere in contemporary Northeast China. The hierarchy of the society from which the language originates deeply influences the language, leading to a system of speech levels and honorifics indicative of the formality of any given situation.

Modern Korean is written in the Korean script (Hangul in South Korea; Chosŏn’gŭl in North Korea), a system developed during the 15th century for that purpose, although it did not become the primary script until the 20th century. The script uses 24 basic letters (jamo) and 27 complex letters formed from the basic ones. When first recorded in historical texts, Korean was only a spoken language; all written records were maintained in Classical Chinese, which, even when spoken, is not intelligible to someone who speaks only Korean. Later, Chinese characters adapted to the Korean language, Hanja, were used to write the language for most of Korea’s history and are still used to a limited extent in South Korea, most prominently in the humanities and the study of historical texts.

Along with other languages such as Chinese and Arabic, Korean is ranked at the top difficulty level for English speakers by the United States Department of Defense.