Sumo Wrestling is a full-contact competitive sport in which a wrestler known as Rikishi tries to force another Rikishi out of the circular ring or into touching the ground with any part of the body other than the soles of the feet. It is the national sport of Japan and is considered to have originated in the country. Japan is the only country in which the sport is practiced professionally and it is a significant part of Japanese culture. Professional matches of the sport are organized by the Japan Sumo Association whose all members (oyakata) are former wrestlers who are the only people to train new wrestlers.
Sumo wrestling matches take place in a circular ring called a dohyo which is 4.55 m in diameter and have an area of 16.26 sq. m. which have a platform made of clay mixed with sand. It consists of two white lines(shikiri-sen) at the center behind which the rikishi (wrestlers) position themselves at the beginning of the bout.
Bouts of sumo wrestling are very short mostlyless than a minute (sometimes only a few seconds). If a bout lasts for more than four minutes, then the referee calls a mizu-iri (water break) after which the wrestlers return to the position from where they left.
The sport is divided into six ranking divisions in which the wrestlers are promoted and demoted based on the merit of their winning/losing records in official competitions. The divisions are: makuuchi, jūryō, makushita, sandanme, jonidan and jonokuchi. Wrestlers enter in the lowest jonokuchi division at the beginning and then work their way up to reach the top division.
Winning the bout
A bout is won by the wrestler if-
The wrestler forces his opponent to step out of the dohyo (ring) or
The wrestler forces his opponent to the ground with any part of the body other than the sole of the feet.