Deuce

In tennis, "deuce" occurs when both players have scored three points each, making the score 40-40. It signifies that the game is tied and requires one player to win two consecutive points to claim the game. After reaching deuce, the player who scores the next point gains an advantage ("ad-in" if serving or "ad-out" if receiving). Winning the subsequent point wins the game. Deuce acts as a critical equalizer, allowing the game to continue until one player secures the necessary two-point lead to win the game.