Deuce

Deuce is a situation that happens when both players earn 40 points in a game. To win a deuce, a player must win two consecutive points. A player is said to have the advantage when he earned one point after the deuce.

When opponents reach a tie score at 40-all, i.e., 40-40, it’s “deuce”, and either player needs to win by two to conclude the game.
The literal translation for deuce is two, stemming from the Latin word “duos”.

In other words, next time you hear “deuce”, think, “win by two”.
The only time players will reach a score of duce during a game is when they achieve a tie score at 40-all.

The first time deuce is reached in a game is when each player has won three points, which ties the score at 40-all. However, we don’t say 40-all; instead, we say deuce.

Once the score is deuce, one player needs to win by two. If the server wins the point at deuce, the score becomes ad-in or the server’s advantage. If the server then loses the next point, the score returns to deuce.

If the person returning wins the point, the score becomes ad-out or the returner’s advantage. If the returner loses the next point, the score returns to deuce once again.

This back and forth repeats indefinitely until one player wins two consecutive points in a row.

Ad scoring, i.e. advantage scoring, where deuce, ad-in, and ad-out are in use, is the standard for competitive tennis, including the pro tour.

In practice or recreational tennis, players will sometimes forego ad scoring and play games that in tennis we refer to as no-ad scoring or sudden death.

In this case, the first player to win four points wins the game. If the score ties at deuce, the next person to win the point wins the game.