A contact sport is any sport where physical contact between competitors, or their environment, is an integral part of the game. Examples include gridiron football, martial arts, and acrobatic sports. Contact may come about as the result of intentional or incidental actions by the players in the course of play. This is in contrast to noncontact sports where players often have no opportunity to make contact with each other and the laws of the game may expressly forbid contact. In contact sports some forms of contact are encouraged as a critical aspect of the game such as tackling, while others are incidental such as when shielding the ball or contesting an aerial challenge. As the types of contact between players is not equal between all sports they define the types of contact that is deemed acceptable and fall within the laws of the game, while outlawing other types of physical contact that might be considered expressly dangerous or risky such as a high tackle or spear tackle, or against the spirit of the game such as striking below the belt or other unsportsmanlike conduct. Where there is a limit as to how much contact is acceptable most sports have a mechanism to call a foul by the referee, umpire or similar official when an offence is deemed to have occurred.
Contact sports are categorised by the American Academy of Pediatrics (AAP) into three main categories: contact, limited-contact and noncontact. In attempting to define relative risk for competitors in sports the AAP have further defined contact sports as containing some element of intentional collision between players. They define such collision sports as being where: "athletes purposely hit or collide with each other or with inanimate objects (including the ground) with great force", while in limited-contact sports such impacts are often "infrequent and inadvertent". While contact sports are considered the most high risk for injury, in some sports being a major feature (such as boxing or other martial arts), limited-contact and noncontact sports are not without risk as injury or contact may come about as a result of a fall or collision with the playing area, or a piece of sporting equipment, such as being struck by a hockey stick or football or even a piece of protective wear worn by a teammate or opposition player.
