Initial sound rule

The initial sound rule (Korean: 두음법칙; Hanja: 頭音法則; RR: dueum beopchik) is series of changes to Hangul, the writing system for the Korean language, made in South Korea to better reflect modern Korean phonology. The changes affect syllable-initial r and n sounds in Sino-Korean vocabulary under certain conditions. In North Korea, the orthography does not recognize this rule, which makes it one of a number of North–South differences in the Korean language.