In tennis, an ace is a legal serve that lands in the service box and is not touched by the receiver, winning the point for the server). A service winner, on the other hand, is a serve that the receiver hits without making a legal return. A player usually hits an ace using their serve speed or direction to beat their opponent. Harder serves are more likely to produce aces, as the opponent has less time to react. Spin and deception can also defeat the returner, and tall players tend to hit more aces than short players because they have more clearance over the net, which helps increase their margin of error when hitting big flat serves. Novak Djokovic, for example, earned 58 second serve aces in 2019, more than anyone else.