In tennis, a "deuce" occurs when both players have a score of 40-40 in a game. This means that neither player has the advantage needed to win the game, requiring one player to win two consecutive points to secure the game. The first point won after deuce is called "advantage," and if the player with the advantage wins the next point, they win the game. If the player with the advantage loses the next point, the score returns to deuce. This back-and-forth can continue until one player finally wins two points in a row, ending the game. Deuce is a critical moment in a match, often leading to intense rallies.