The scoring system in tennis has mystified many, and the true origin of this unusual scoring system is still not clear.
The scores go from 0, 15, 30, 40 then game (60). The sequence of multiples of 15 is clear except for the 40, which may have been abbreviated from 45 for simplicity in calling out the score.
A score of love for zero points is a reference to the zero looking like an egg, which the French call 'œuf', which to the uneducated English sounds a lot like 'love'
Deuce, indicating two or a pair, is when both players are on a score of 40.
After the score has reached 40-all, the winner of the next point will have the advantage, requiring another point to win the game. If the player with advantage loses the next point, the score reverts to 40-all.
Service and Scores
As the first service is always from the right side fo the court, to the opponents right side, knowing where you are serving from can help you remember the score, and vice versa. See more about scoring and serving.