A slice serve is one of four types of serves (slice, flat, kick, and underhand) that is utilized in tennis. A serve is what begins each point and involves a player tossing the ball into the air and hitting it over the net. The ball must land within the opposite service box. What sets a slice serve apart from the other serves is the large amount of side spin that it places on the ball as well as a slow speed
In order to hit a slice serve, a player must toss the ball further away from their body, both to the side and in front of them. The goal is to create spin, and that is accomplished by striking the side of the ball with the racket.
To enhance the effect the body moves forward and the hips and shoulders should rotate to the side. The racket is held with a continental grip to allow for the face of the racket, the strings, to reach the side of the ball furthest from the player. The follow through is also important as it is what accentuates the slicing motion generating more side spin.
The name of the serve can be explained by the motion of the racket chopping down through the air. It is comparable to slicing food with a knife.
Here's an image showing how to perform a slice serve toss and how to make contact with the ball.
In comparison to the most commonly used serve, the flat serve, the slice serve will skid across the tennis court instead of bouncing up, and the ball will travel slower.
The unconventional bounce is the result of the number of rotations the tennis ball has in midair. On each of the three traditional surfaces in tennis (grass, clay, hardcourt) the serve will generate a different bounce. The speed of the surface impacts the success of the slice serve. Grass surfaces are the fastest of the three, followed by hardcourt, and then clay.
Friction and surface area explain why slower surfaces are less effective. A "slow" surface such as clay will interact with more of the ball's surface area and there will be more friction placed on the ball. This leads to a higher bounce and less spin on the ball after contact with the ground.
The different bounce explains why a slice serve is most effective on grass. The bounce, which is better described as a skid, will have more speed and in result causes more side to side movement. The unique nature of the side to side bounce makes it extremely unpredictable and a useful way to keep the opponent guessing and off balance.
Here's a graphic depicting the differences in speed each surface has and how the ball will bounce as well.
It can be used as an offensive weapon with the correct placement as it can be difficult to return. A right-handed player serving to the deuce court (the left service box and starting point for odd points) can put the opponent in a defensive situation with a well-placed ball. Their serve would end up bouncing and moving towards the alley, away from the opponent. The opponent is then in a position where they need to move and then stretch to make contact with the ball rather than setting their feet and driving through it.
Left-handed players are generally regarded as having a more effective slice serve than right-handed players. That can be explained by the fact that the large majority of tennis players are right-handed. So when a left-handed player uses a slice serve the ball will bounce towards the right-handed opponent's backhand, which is in most cases is weaker than their forehand.
The most important part of the slice serve is placement. While a flat serve is best if it is fast, a slice serve is at its best when it is hit in the right spot. Nearly all players focus on perfecting the angle at which their serve delivers the ball to the opponent. Most will execute the slice serve towards the alley (out wide serve) but a slice serve to the returner's body is also effective.
Because the emphasis of the serve isn't speed, it can be a good choice for a player if in a high-pressure moment they have to slow down their serve in order to get the ball in. It is a more consistent serve than a flat serve. A tennis ball is easier to control when it is hit softly, giving the server a larger margin of error in a potentially tense situation. Another benefit is that the amount of spin prevents the server from receiving a hard hit ball back at them even when their serve is slower.