"خط کناری" refers to the boundary line in various sports, such as فوتبال and بسکتبال, that marks the limits of the playing area. When the ball crosses this line, it is considered out of play, leading to specific rules for resuming the game, such as throw-ins or out-of-bounds plays. In addition to sports, "خط کناری" can also describe the edges or borders of any defined space, such as a field or a plot of land. Understanding these boundaries is essential for maintaining order and ensuring fair play in competitive environments.