A serve (or, more formally, a service) in tennis is a shot to start a point. The serve is usually initiated by tossing the ball into the air and hitting it (usually near the apex of its trajectory) into the diagonally opposite service box without touching the net. It may be performed underhand or overhead. The serve is the only shot where a player can take his time to set up, instead of having to react to an opponent's shot.
The serve is one of the more difficult shots for a novice, but once mastered it can be a considerable advantage. Advanced players can hit the serve in many different ways and often use it as an offensive weapon to gain an advantage in the point or to win it outright. Because of this, professional players win most of their service games, and breaking serve plays a crucial role in a match.
If the ball hits the net cord but lands in the service court, this is a let service, which is void and the serve is replayed, and the server is allowed either 1 or 2 serves depending on whether the let occurred on the first or second serve. A ball that hits the net cord but lands out is a fault.
The server is required to keep his or her feet in nearly the same position during the serve. The server's feet may be raised off the ground, but walking or running is not permitted. This prevents the opponent from being misled as to where the serve will originate. Breaching this rule or exceeding the permitted part of the court constitutes a foot fault.
A player unsatisfied with his or her toss can let the ball fall to the ground and try again. If the server swings the racquet and misses the ball, it is called a fault. If the server does make contact with the ball (as with a body part or the racquet) on an errant toss, it is only a fault if the server attempted a swing.
The term "kick serve" is ambiguous. Many use it as a synonym for "twist serve." But most use the term "kick serve" to refer to any serve with heavy topspin on it - that is, the topspin serve and the twist serve.
Each type of serve has its tactical advantages. By varying the type of serve and its placement, the server gains the advantage in delivering a great variety of serves.
The flat serve and the slice serve are used primarily as first serves, because they have a small margin for error but are most likely to ace or force an error. Second serves usually have topspin on them, which makes them much less likely to land in the net or out. Topspin serves like the twist serve also make a good change-up as a first serve.
A flat serve must come close to the net, so it has a small margin for error. Therefore, flat serves are most often hit straight down the center, where the net is lowest, and they usually are delivered as first serves, when the server can afford the risk of faulting.
The topspin on the ball also makes it bounce high. Many receivers handle the high bounce well on their forehand side but not on their backhand side. Therefore, placed to the backhand, topspin serves are useful for serve and volley play, even on the first serve.
The topspin serve is harder to learn than the flat serve and the topspin-slice serve, as the contact point is directly over the server's head or perhaps even a little behind it, requiring complex body mechanics. It is hit with a Continental grip or an Eastern Backhand grip (using the forehand side of the racket face).
A sliced serve's sidespin causes the ball to curve leftward and skid when it bounces, curving further leftward after the bounce. A good slice serve curves so much that it can draw the receiver ten feet wide of the singles sideline to play the ball.
A severely sliced serve is sometimes called a "sidespin" serve or a "slider."
Since a slice serve has little or no topspin on it, it cannot be aimed high over the net and has little margin for error. So, it is generally used only as a first serve. It can be used to ace the receiver, to draw the receiver off the court and out of position, or to "jam" the receiver with a serve curving sharply into his or her body.
This blend of topspin and sidespin makes the ball curve downward and leftward in flight, bouncing high and continuing to curve leftward.
Because of the topspin on it, a topspin-slice serve can be aimed higher over the net than a slice serve or a flat serve. So, it has a greater margin for error.
The twist serve was originally known as the "American twist" serve, and it is still sometimes referred to by that name. It is a special kind of topspin-slice serve that behaves differently after the bounce because it has much more topspin than sidespin on it. So, instead of skidding and continuing to curve leftward after the bounce like a slice serve, it "grabs" the court and breaks rightward in the direction of a right-hander's backhand. Like all spin serves, it is hit higher over the net with a larger margin of error. This along with the awkward bounce, make it a popular second service choice.
To create this action the ball needs to have a twisted axis of rotation, so that the ball's spinning is out-of-line (axis of spin rotated slightly clockwise from a top view) with its flight path. To execute this serve, a continental or, more commonly, an Eastern backhand grip is used. The ball is thrown somewhat behind and to the left of the server's head, and the racquet brushes the ball from the 8 o'clock position to the 2 'clock position (although other players can have a 7 o'clock to 1 o'clock stroke), imparting a combination of topspin and sidespin. Different angles of attack by the racquet on the ball varies the action of the kick, making it less predictable.
These additional terms are often used in the media.