The typical sport that uses the term, "deuce", is Tennis or Table Tennis.
Switch every 2 serves. In deuce, switch every serve.
In tennis, when both opponents are tied at 40-40, the score is called deuce. Deuce changes to advantage when one opponent scores after achieving deuce.
Deuce is basically a way to win by two points in a match such as tennis or table tennis. You get an 'advantage' when you win your first point, and have to win the second point in order to win the game. If you lose your second point, it'll go back to deuce until somebody wins by two points.
Deuce is where both players are on 40 in a match of tennis
tennis
The term is called "Deuce."
40:40 Deuce in Tennis
4040 is deuce in tennis
40-40
Deuce.
Deuce