A K.O. (Knockout) occurs in combat sports, such as boxing and mixed martial arts, when a fighter is rendered unable to continue the match. This typically happens when a competitor is struck with a powerful blow that causes them to fall to the ground and remain there, often unconscious or unable to rise before the referee counts to ten. In a K.O. situation, the referee plays a crucial role in ensuring the safety of the fighters. They will immediately stop the fight and assess the downed fighter's condition. A K.O. can be a decisive and dramatic moment in a match, often leading to a victory for the attacking fighter.