Ball, football

A football is an inflated ball used to play one of the various sports known as football. The first balls were made of natural materials, such as an inflated pig bladder, sometimes inside a leather cover. (This has given rise to the United States slang-term "pigskin".) Modern balls are designed by teams of engineers to exacting specifications, with rubber or plastic bladders, and often with plastic covers. Various leagues and games use different balls, though they all have one of the following basic shapes:

1. a sphere: used in Association football (also called soccer in some countries) and Gaelic football
2. a prolate spheroid ('egg-shaped')
   • either with rounded ends: used in the rugby codes and Australian football
   • or with more pointed ends: used in American football and Canadian football