A knockout (also referre to as a K.O.) is a winning criterion in several full-contact combat sports, such as boxing, kickboxing, Muay Thai, mixed martial arts 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. 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 himself, or the fighter's cornermen) decide that a fighter cannot continue the match, even though he did not fail the count.British records refer to TKOs as either "retired", if the fighter refuses to continue, or "R.S.F.", for Referee Stopped Fight.