Korean (, see below) is the official language of both South Korea and North Korea, as well as one of the two official languages in China's Yanbian Korean Autonomous Prefecture. About 80 million people speak Korean worldwide. For over a millennium, Koreans wrote with adapted Chinese characters called hanja, complemented by phonetic systems like hyangchal, gugyeol, and idu. In the 15th century, Sejong the Great commissioned a national writing system called Hangul, but it only came into widespread use in the 20th century, because of the yangban aristocracy's preference for hanja.