What is “deuce” in tennis?
Deuce is when the score in a game is equal to 40-40, or both players have won three points each. At that stage one player has to win by two points to win the game. So if Sharapova and Vaidisova are playing and the score is deuce, Sharapova will have to win one point (making it Advantage Sharapova) and then another to win the game. If she loses that second point, the score goes back to Deuce.