An Ace in tennis is a serve that lands in the service box and is not touched by the receiver. This results in the server winning the point immediately.
Aces are usually hit with a lot of power and speed. The ball often lands near the corners or edges of the service box. This makes it very hard for the receiver to reach the ball in time.
Many professional tennis players are known for hitting a lot of aces. Some famous examples include John Isner, Ivo Karlović, Roger Federer, and Serena Williams.
Aces can happen on either the first or second serve. But they are more common on first serves, where players can hit with maximum power.
Top 10 Fastest Aces In Tennis History – [Ace][1]
[1]: https://www.youtube.com/watch?v=UMzVQOmPacs