Tennis is a racquet game which belongs to the category of racquet sports. Tennis can be played between either two teams ("doubles") or two players ("singles"). Since tennis is a racquet sport players use stringed racquets to hit a ball (which, by the way, is rubber, hollow and covered in felt) over the net into the opponent's half of a court. Sometimes in some places tennis is called lawn tennis in order to tell it apart from real tennis which is also known as court tennis or royal tennis and is older type of the game played indoors on absolutely different kind of a court. Tennis was originated in England in the 19th century and spread first all through the English-speaking people, especially among the upper human classes.

Today tennis is one of Olympic sports played by all ages and at all levels of society in many countries throughout the world. The rules of the game have remained outstandingly unchanged since the early 19th century. Millions of people are a fond of tennis as a very spectator sport along with millions tennis players. The biggest popularity over the years have gained four Grand Slam tournaments.

Speaking about tennis ball rules, it must be said that not all balls are allowed in tennis play especially on professional tennis tournaments. Tennis balls approved for playing under the tennis rules must be in conformity with the latest specifications approved by International Tennis Federation (ITF). Only ITF can decide whether a ball or its prototype meets the specifications of tennis rules and either approved for play or not.

Here are some of the tennis ball rules adopted by International Tennis Federation and being in effect today:
1) Tennis ball must have uniform outer surface which must consist of a fabric cover and be yellow or white in color. All seams on the ball surface, if any, must be stitchless.
2) Any ball must comply with the weight requirements and be of more than 56 grams and less than 59.4 grams.
3) There are more that just one type of ball specified. Each tennis ball must have a bound of 53 inches or more but less than 58 inches when dropped upon a rigid, flat such as concrete for example.
4) Tennis ball rules stipulate that two additional ball types can be used for play in the area that is 4,000 feet above the sea level.
5) For ball to comply with tennis ball rules, all tests for size, deformation and bound must be conducted in accordance with regulations passed by International Tennis Federation.

And here are some more tennis ball rules but this time concerning directly the gameplay:
1) Ball in play. Unless a let or a fault is called, the ball is considered to be in play from when a server hits the ball until the point is decided.
2) Ball touches a stable fixture. If the ball should touch a permanent fixture after touching a proper court, the player who sent this ball wins a point. Alternatively, if the ball should touch such fixture prior to the hitting the ground, the player who delivered such a ball loses a point.
3) Ball touches line. Should a ball touch a line, it is deemed as touching the court that is bounded by this line.