Wrestling is the act of physical engagement between two people in which each wrestler strives to get an advantage over, or control of, the opponent. Physical techniques which embody the style of wrestling are clinching, holding, locking, and leverage. Avoiding techniques likely to lead to serious injury, the basic principles of wrestling are closely related to those of military hand-to-hand combat or self-defence systems. Many styles of wrestling are known all over the world and have long histories. Amateur wrestling has been an Olympic sport for over one hundred years and professional wrestling is a popular form of entertainment as well as an art form.