What must happen for the ball to be considered in play?

For the ball to be considered in play, it is essential that it must be kicked and clearly move. This is rooted in the Laws of the Game, which specify that the ball is in play when it is properly kicked and starts traveling in a clear direction. The motion of the ball indicates that it is actively part of the game, allowing players to engage with it.

While throwing in a ball, such as during a throw-in, also places it in play, simply throwing it does not encompass all scenarios where the ball can be in play, as it may not involve movement or clear intent. Contacting the goal post does not inherently mean the ball is in play; it might rebound but isn't necessarily involved in active play unless it has been kicked or passed into the general play area. Additionally, the touching of the ball by two players does not mean that the ball is in play unless it is kicked or moved in a way that satisfies the criteria for active play.

Thus, the requirement of kicking and moving the ball provides the most accurate and universally applicable criterion for determining when the ball is considered in play.