Sumo is one of wrestling as a sport wrestler (Rikishi) must try to force your opponent out of the ring (Dohyo) or force the rest of the competitors, with the exception of the foot contact with the ground.
Sumo is a form of wrestling. Sport is the wrestlers (Rikishi) to try to force the opponent out of the ring (Dohyo) or force the rest of the competitors, except for the feet touch the ground.