Tee ball or t-ball is a sport based on baseball and is intended as an introduction for children to develop baseball skills and have fun. The name "Tee Ball" is a registered trademark, while t-ball is the generic name, although many sources use tee ball as a generic title.

In t-ball, the pitcher is usually used for defensive purposes only. The ball is placed on an adjustable tee atop the home plate at a suitable height for the batter to strike. (In some clubs, adult coaches give the batter an opportunity to try and hit a few pitched balls before going to the tee in the hope that this will further develop batting skills.) Most of the other rules are similar or identical to those of baseball, though the game is played on a smaller field.

In many organizations, score is not kept and rules are designed to maximize participation: an inning is completed once each child has had a turn at bat and all extra players of the defensive team play in the outfield every inning. (In some clubs, an inning is played similar to baseball, which is once the defensive team has made three outs, the team at bat plays defense and the defensive team takes the bat.) To encourage the defensive team to try to make plays, there are typically no extra bases on overthrows and runners may not advance after the ball is in possession of an infielder.

A tee is a stand used to support a stationary ball so that the player can strike it, particularly in golf, tee ball, American football, and rugby.

The word tee is derived from the Scottish Gaelic word tigh meaning house and is related to the 'house' in curling (the coloured circles). This would make sense, as the first golf tees were within a circle of one club length round the hole. Nowadays, modern courses have separate, designated tee boxes for each hole. For example, the ninth hole of a course is played from the ninth tee to the ninth green, and similarly for the other holes.

In golf, a tee is normally used for the first stroke of each hole. The area from which this first stroke is hit is informally known as the teeing ground. Normally, teeing the ball is allowed only on the first shot of a hole, called the tee shot, and is illegal for any other shot; however, local or seasonal rules may allow or require teeing for other shots as well, e.g., under "winter rules" to protect the turf when it is unusually vulnerable. Teeing gives a considerable advantage for drive shots, so it is normally done whenever allowed. However, a player may elect to play his/her tee shot without a tee. This typically gives the shot a lower trajectory.

A ball is a round, usually spherical but sometimes ovoid, object with various uses. It is used in ball games, where the play of the game follows the state of the ball as it is hit, kicked or thrown by players. Balls can also be used for simpler activities, such as catch, marbles and juggling. Balls made from hard-wearing materials are used in engineering applications to provide very low friction bearings, known as ball bearings. Black powder weapons use stone and metal balls as projectiles.

Although many types of balls are today made from rubber, this form was unknown outside the Americas until after the voyages of Columbus. The Spanish were the first Europeans to see bouncing rubber balls (albeit solid and not inflated) which were employed most notably in the Mesoamerican ballgame. Balls used in various sports in other parts of the world prior to Columbus were made from other materials such as animal bladders or skins, stuffed with various materials.

As balls are one of the most familiar spherical objects to humans, the word "ball" is used to refer to, or to describe, anything spherical or near-spherical.