A yellow card in football is a disciplinary card shown by the referee to a player as a warning for committing a misconduct. It serves as an official caution to the player and is typically shown for actions such as unsporting behavior, dissent, or persistent fouling. When a player receives a yellow card, it is recorded by the referee and the player may face further disciplinary action if they receive additional yellow cards in the same match. If a player accumulates a certain number of yellow cards over the course of the season, they may also face a suspension. The yellow card is displayed by the referee by holding it above the head or showing it to the offending player. It is considered to be a way to maintain discipline and fair play in the game.