Idu is an archaic writing system that represents the Korean language using Chinese characters ("hanja"). The script, which was developed by Buddhist monks, made it possible to record Korean words through their equivalent meaning or sound in Chinese.

Korean is the native language for about 81 million people, mostly of Korean descent. It is the official and national language of both North Korea and South Korea. The language has notable differences in each of the Koreas, in part owing to different official standardizations of the language. They are still largely mutually intelligible, however. South Korean newspaper Daily NK has claimed North Korea criminalizes the use of the South's standard language with the death penalty, and South Korean education and media often portray the North's language as alien and uncomfortable.