is a method of annotating Classical Chinese so that it can be read in Japanese that was used from the Heian period to the mid-20th century. Much Japanese literature was written in this style, and it was the general writing style for official and intellectual works throughout the period. As a result, Sino-Japanese vocabulary makes up a large portion of the lexicon of Japanese, and much classical Chinese literature is accessible to Japanese readers in some semblance of the original. The corresponding system in Korean is gugyeol (口訣).