Boxing is a combat sport in which two participants, generally of similar weight, fight each other with their fists. Boxing is supervised by a referee and is typically engaged in during a series of one to three-minute intervals called rounds. There are three ways to win. Victory is achieved if the opponent is knocked out and unable to get up before the referee counts to ten seconds (a Knockout, or KO) or if the opponent is deemed too injured to continue (a Technical Knockout, or TKO). If there is no stoppage of the fight before an agreed number of rounds, a winner is determined either by the referee's decision or by judges' scorecards.
Although fighting with fists comes naturally to people, evidence of fist-fighting contests first appear on ancient Sumerian, Egyptian and Minoan reliefs. The ancient Greeks provide us our first historical records of boxing as a formal sport; they codified a set of rules and staged tournaments with professionals. The birth hour of boxing as a sport may be its acceptance as an Olympic game as early as 688 BC. Modern boxing evolved in Europe.