In the game of tennis, there are four commonly used serves: the "flat serve", the "slice serve", the "kick serve", and the "underhand serve".[citation needed] Slice serves can be hit with spin to either the left or the right, and this distinction is often utilised to make the serve unpredictable and throw the opponent off balance. All of these serves are legal in professional and amateur play. The term kick serve is ambiguous. It may be used as a synonym for the twist serve or the American twist. However, kick serve is commonly used to refer to any serve with heavy topspin or kick on it. Servers can gain a tactical advantage by varying the type of serve and the ball's placement. The flat serve and slice serve are used primarily as first serves because they are more likely to yield an ace or force an error, although they require high accuracy. Second serves usually have topspin or kick on them, which makes them less likely to land in the net or out of bounds. Kick serves also make a good change-up[clarification needed] as a first serve. Flat serve A flat serve is hit with a Continental grip (holding the racket as if it were an axe) and a swing path directly through the ball, which causes the ball to cut quickly through the air without spinning. Some professional players can hit flat serves at speeds near 150 miles per hour (240 km/h).[citation needed] A flat serve must come close to the net therefore having a small margin for error. Therefore, flat serves are usually hit straight across the center, where the net is lowest. They are usually delivered as first serves, when the server does not risk a double fault. The ball is thrown straight above for the optimal serving point. Slice/reverse slice serve A slice serve is hit with sidespin, which requires the server to brush the back of the ball toward their dominant side with the racket. It is commonly hit with the Continental grip or the Eastern backhand grip (using the forehand face of the racket). The ball is thrown slightly to the dominant side of the server then is struck laterally on the server's dominant side. For a right-handed player, a sliced serve's sidespin causes the ball to curve leftward. When the ball bounces, it skids and curves farther leftward. The curve of a good slice serve can draw the receiver 10 feet (3.0 m) wide of the singles sideline to play the ball.[citation needed] 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. Therefore, it is generally used as a first serve. It can be used to ace the receiver, to draw the receiver out of position, or to "jam" the receiver with a serve curving sharply towards his or her body. In professional and amateur tennis, the reverse slice serve is rarely used except as a novelty. As the word reverse is defined, one must hit opposite to the side and opposite to the path of the slice struck serve. Kick/American twist/Reverse kick serve Holcombe Ward and Dwight Davis introduced the kick/American twist serve in the late 1800s. The kick serve is generated by tossing the ball over the head, then hitting it laterally on the server's non-dominant side brushing upward toward the dominant side. When hit correctly, the ball clears the net in a high arc with heavy topspin, causing the ball to dive into the service box. Upon hitting the surface of the court, the ball may bounce high directly toward the receiver for a kick serve, or to the left for the receiver for an American twist serve. The physics of the spinning ball in flight involves the Magnus effect because the spinning ball creates a whirlpool of air around itself. The Twist Serve is a more extreme version of the Kick Serve, which involves more brushing of the ball from the 7-8 o clock position to the 1-2 o clock position, and faster swing speeds. If performed exceptionally, it can completely change the direction of the ball movement away from the other player, although this requires a very strong and flexible back. In professional and amateur tennis, the reverse kick/American twist serve is rarely used except as a novelty. As the word "reverse" is defined, one must hit opposite to the side and opposite to the path of the kick struck serve.

• published: 14 Feb 2015
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