What is an ad in tennis?

Answer 1

Okay, so lets say it was deuce. Then I was the server, and I won the point you call it ad-in meaning its MY advantage.. But if you win the point, it's called ad-out- that means its YOUR advantage.

Answer 2

Ad means advantage. It is the score in a game. For example if I say ad in, I can win the game if I win the point. If you lose the point the score will go back to deuce.