Judo is a martial art that originated in Japan. It is one of the official Olympic events.
Judo includes a variety of rolls, falls, throws, hold-downs, chokes, joint-locks and strikes. But the main focus is on nage waza (throwing) and ne waza (groundwork).
Judokas are divided into groups according to their weight. The objective of a judo player is to score an ippon, and win the match.
There are three ways to score an ippon:
1. Throw the opponent - with enough power and control - so that he lands mainly on his back
2. Pin the opponent to the ground, with his back on the mat (groundhold), for 25 seconds
3. Force the opponent into a choke, strangle or an armlock
Judokas can score through ippon, waza-ari, yuko and koka. A waza-ari is awarded for a throw that does not have enough power or control to be considered an ippon. It is also awarded for a hold of 20 seconds. Two scores of waza-ari are equal to an ippon which would win the match.
Yuko (15-second groundhold) and koka (10-second hold-down) get less points, and only count as tie-breakers. Unlike waza-ari, those scores cannot be added on.
When the time is up, the judoka who has scored the most number of points wins the match. In international competitions, including the Olympics and World Championships, men's matches last five minutes. For women, it's four minutes.
Judo has seven ranks. The highest is black, followed by brown, blue, green, orange, yellow and white.