A ball is a round object (usually spherical but sometimes ovoid) 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. In the context of sports, "ball" need not refer to a spherical object, as is the case
in American football. 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. Blackpowder weapons use stone and metal balls asprojectiles.