A knockout (also referred to as a K.O.) is a winning criterion in several full-contact combat sports, such as boxing, kickboxing, Muay Thai, mixed martial arts, Karate and others sports involving striking. A knockout is usually awarded when one participant is unable to rise from the canvas within a specified period of time, typically because of fatigue, injury (serious or temporarily incapacitating, e.g. a bleeding cut above the eye can blind a fighter), loss of balance, or unconsciousness; that is, the person may literally be knocked out. A technical knockout (also referred to as a T.K.O.) is often declared when the referee or other judges (such as official ring physician, the fighter, or the fighter's cornermen) decide that a fighter cannot continue the match, even though he did not fail the count; or, in many regions, a fighter has been knocked down three times in one round. British records refer to TKOs as either "retired", if the fighter refuses to continue, or "R.S.F.", for Referee Stopped Fight. In amateur boxing, a knockout is scored as "RSC," for Referee Stopped Contest. A technical knockout ("Outclassed") can also be declared if a fighter is ahead by 15 points in a bout.