What does ACE mean?

Ace ball refers to the service score in tennis.

In tennis, the ACE ball serves one of the two sides of the game. The ball falls in the effective area, and the opponent doesn't touch the ball, so let the ball score directly. If the opponent touches the ball out of bounds or under the net, it's just a serve score, not an ACE ball.

Serving ACE ball needs to combine speed, landing point and tactics, which can be met but not sought. It is often seen that some famous athletes promise to donate a certain amount of money for every ace ball played in major competitions, which is also a combination of the charm of the competition and the humanistic spirit.