Sumo has a history that dates back since the beginning of Japan. There have been many rules and systems that have been abolished or replaced. The list below are just the major changes since the Edo Period.
Azukari (預り): Hold or no decision, a kind of draw. After a mono-ii, the gyoji or the shimpan "holds" the result if it was too close to call. Recorded with a white triangle. In 1927, the system was abolished and a torinaoshi (rematch) now takes place instead; the last azukari was recorded in 1951.
Hikiwake (引分): A type of draw caused by a long bout that exhausted both wrestlers beyond the point of being able to continue. Also possibly known as a yasumi (休み). In modern sumo, this situation is resolved with a break and subsequent restart or rematch. Though common in early sumo, hikiwake are very rare in the modern age and have not been declared since 1974. Recorded with a white triangle.
Itamiwake (痛み分け): A draw due to injury. A rematch (torinaoshi) has been called but one wrestler is too injured to continue; this is no longer in use and the injured wrestler forfeits instead. The last itamiwake was recorded in 1999. Recorded with a white triangle.
Kosho Siedo (公傷制度): Public Injury System. Introduced in 1972, this system allowed a wrestler who had been injured in the ring during a tournament to sit out the next tournament without any effect on his rank. It was abolished at the end of 2003 because it was felt too many wrestlers were missing tournaments with minor injuries.
Mushobu (無勝負): No Result. A kind of draw; the gyoji doesn't count a win or a loss. This outcome was recognised in the Edo period.
Shinjo (新序): A designation given to wrestlers who had performed well in maezumo that allowed them to participate in jonokuchi in the same tournament. Additionally, if they performed well at this stage, they were allowed to skip straight to the jonidan rank in the next tournament. This system is no longer used.