The dan (段) ranking system is a Japanese mark of level, which is used in traditional fine arts and martial arts. Originally invented in a go (board game) school in the Edo period, this system was later applied to martial arts by Kanō Jigorō, the founder of jūdō and later introduced to other East Asian countries.
In the modern Japanese martial arts, holders of dan ranks often wear a black belt. Dan ranks are still given in arts such as the strategy board games go (碁) and renju (連珠), the art of flower arrangement (ikebana), and tea ceremony.
The character of dan (段 dan ) is used in Japanese to mean step or grade, and is commonly equated with degree. However, the origin of the Chinese character, pronounced duán in modern Pinyin, was used mean "phase". Dan rank is often used along with the lower rank system, kyū (級) rank. There are other methods of assessing rank in Japanese martial systems, of particular note is the older, menkyo system.