What is the primary purpose of the throw-in according to its governing law?

The primary purpose of the throw-in, according to the Laws of the Game, is to restart play after the ball has completely crossed the touchline, thereby going out of bounds. When this occurs, the game is paused, and the throw-in serves as the means to bring the ball back into play. It is executed by a player from the team that did not touch the ball last before it went out, and specific rules govern how the throw-in must be taken. This ensures continuity in the game while also maintaining fair play and establishing a clear process for reintroducing the ball.

The other options refer to different scenarios in the game. For example, restarting play after an injury is typically done through a drop ball or an indirect free kick rather than a throw-in. Similarly, a goal kick restarts play after the ball goes out of bounds over the goal line, and player substitutions are managed through a different set of rules entirely, aimed at changing players rather than restarting the game. Thus, the throw-in’s unique purpose is explicitly tied to situations where the ball has left the field of play across the touchline.