# Does calling 30-30 "deuce" in tennis affect the game scoring?

As an IT guy I cannot avoid the observation that the states "30-30" and "40-40", "deuce", have the same outgoing transitions in the state machine "tennis game": From both scores a two point difference is necessary to win the game, and the state machine degenerates to a machine with three states (advantage for either of the two players, or deuce). Likewise, "30-40" and "40-30" is "advantage" for the respective leader.

My son and I therefore started calling "30-30" "deuce" and "30-40"/"40-30" "advantage", first jokingly, and now as a matter of routine. As with traditional counting, a win requires scoring at least four times and being two scores ahead.

This habit does not change the game, right?

Edit to address closing as dup: The alleged duplicate is an entirely different question. It asks in effect why we don't count 1, 2, 3 instead of 15, 30, 40 but does not address the fact that there is no logical distinction between 30-30 and 40-40 (or 2-2 and 3-3, for that matter).

You are correct that 30-30 and 40-40 are the same, as far as the potential future outcomes for a game are concerned. One player must win by two from that point (assuming ad scoring).

One answer to the question in the title, 'Is there a reason that in tennis 30-30 is not called “deuce”?' is that it is what is written in the rules. For example, the USTA's guide to scoring explicitly says that "Deuce" is 40-40.

However, I think the real answer can be summed up in one word: Tradition. Tennis has been around for hundreds of years. A score of 30-30 has long been referred to as "30-30" or "30 all", but 40-40 has long been referred to as "Deuce". There is no compelling reason to change and many folks like things the way they are, while changing things now would confuse some people - at least for a little while.

That said, the fact that the score is the same in a state machine has been recognized for some time. Injuries caused me to stop playing, but when I played a few decades ago, I did know people who would give the score as "Deuce" or "30-Deuce" at 30-30.

Deuce connotes that both players have scored their maximum per game without winning the game. Calling 30-30 'deuce' does not reflect this. Similarly, using 'advantage' before true deuce has been attained does not indicate that both players have scored their game max without winning the game.

• You say essentially that "Deuce" denotes 40-40 and not 30-30; that was clear to me. What I wondered was whether applying the "Deuce/Advantage" "paradigm" and terminology to 30-30 and 30-40, respectively, changes anything with respect to the factual rules (other than words uttered). Specifically, is there a sequence of events which could lead to a different outcome under the respective counting methods. I think not, but I'm getting humbler with age. Aug 7, 2019 at 16:24

This habit does not change the game, right?

You're right, this does not affect who wins a game. It'll change the statistics (sometimes, if you watch a match on television, you see something like "Deuce #9" if it's a particularly long game - your scoring method would add one extra to that count). Another equivalent way to look at a tennis game is that it's best-of-6-must-win-by-2-points.

With regard to "40-40": in court tennis (aka real tennis), when the handicap system is used "40-all" is called instead of "deuce" because the next point will win the handicapped game. In non-handicap play, as in lawn tennis, one needs to win by two points, so "deuce" (derived from deux (two)) is called to indicate this.