Association football, commonly known as football or soccer, is a sport played between two teams of typically eleven players, though other variations in player numbers such as 5 and 7 are also played, with a spherical ball. At the turn of the 21st century, the game was played by over 250 million players in over 200 countries, making it the world's most popular sport.[1][2][3][4] The game is played on a rectangular field of grass or green artificial turf, with a goal in the middle of each of the short ends. The object of the game is to score by kicking the ball into the opposing goal.