If a player gains the advantage and then loses the next point, the score returns to deuce. So in order to win the game from deuce, a player must win two points in a row. When the serving player has the advantage, the score may be called “ad in,” and called “ad out” when the returning player has the advantage.
Sometimes tournaments will use a “no-ad” scoring system. In this system, a game is won simply by whoever first wins four points—at deuce, a sudden death point is played. In order to differentiate the scoreline of games in the set from the scoreline of points within the game, “15” is used to mean one point, “30” to mean two points, and “40” to mean three points. At 40-40, the score is called deuce. When a player has no points, it is written as “0,” but called “love.”
The server’s score is always called first. For example: if the server has won one point in this game, and the returner has won two points, the score will be called 15-30. If the server has won three points and the returner has not won any, the score will be called 40-0, which sounds like “Forty-Love.”