A tennis ball is a green or white ball designed for the sport of tennis, a little smaller than a cricket ball or baseball.  The tennis ball is special because at the speed it travels, it lies around the border of being both predominantly laminar and predominately turbulent.  Because of the topspin, the tennis ball is moving very quickly downward with gravity.  It is usually colored yellow or white and is about two inches in diameter. 

Modern regulation tennis balls are kept under pressure (approximately two atmospheres) until initially used.  In the early days of tennis, balls were often made of leather stuffed with hair or wool.  Early tennis balls were made by Scottish craftsmen.  These tennis balls were commonly made from a wool-wrapped stomach of a sheep or goat and tied with rope.  In the 18th century, ¾" strips of wool were wound tightly around a nucleus made by rolling a number of strips into a little ball.

The tennis balls are very well engineered.  The ball compresses about 3 mm when dropped from 100 inches above the tennis racquet.  If the ball did not lose any energy, it would be very fast and harder to control when playing the game of tennis.  If the balls velocity is increased, the fraction of the energy lost also increases because of the greater collision between the tennis racquet and the tennis ball.

With the introduction of lawn tennis in the 1870s, vulcanized rubber was first used to manufacture balls, often in tubes of four with a package, but not with the name of the brand.

Tennis balls must conform to certain criteria for size, weight, deformation, and bounce criteria to be approved for regulation play.  The most important test for amateur players is the bounce test, as tennis balls begin to lose their bounce as soon as the tennis ball can is opened.  Most Tennis players prefer tennis balls with good bounce, extra duty, and can be used on all types of courts.

Tennis balls are filled with air and are surfaced by a uniform felt covered rubber compound.  The balls are steam-fluffed to raise the nap, thus ensuring that they react better to the court surface and racquet.  The finished balls are tested for uniformity of bounce and deformation, durability of the cover, as well as flight, impact, wear and resistance characteristics to ensure that every ball precisely meets the International Tennis Federation's specifications in the Rules of Tennis.  Tennis balls are subject to strict regulations governing their size, mass, bounce, compression and construction properties.  Despite these regulations, their condition can be changed significantly through play and elite tournaments regulate how often new balls are introduced to play.  Unfortunately, abnormal ball wear and unacceptable balls result in a cost to manufacturers through returns and a loss of brand reputation.  Currently, manufacturers evaluate tennis balls on a subjective scale with regards to the condition of their cloth cover.  This process is wholly dependent on the person visually inspecting the balls, and no quantitative performance information can be determined.