Hockey, (field), an 11-a-side stick-and-ball field game. It is also played indoors with 5-, 6-, or 7-a-side.
A standard field or pitch may be of various surfaces (there are all-weather, artificial pitches) but is traditionally grass. The goals are 4 yd (3.66 m) wide and 7 ft (2.13 m) high. A hockey stick may be of any length to suit an individual player but it must weigh between 12-28 oz (340-794 g). The head may not be more than 4 in (10 cm) long and it must be of wood. It has a flat face on its left-hand side and rounded edges. The diameter of a legitimate stick is gauged by whether or not it will pass through a ring 2 in (5 cm) in diameter. The ball may be of any material, sewn or seamless. It should weigh about 5y oz (160 g) and have a circumference of about 9 in (23 cm). A game lasts 70 minutes (35 minutes each way) with a half-time interval of 5 to 10 minutes. It is controlled by two umpires, one for each half of the field mostly remaining outside the field of play.

Originally, all teams played with five forwards, supported by three halves and two backs, plus a goalkeeper. Gradually other systems evolved leading to a variety of more flexible formations, with players usually classified simply as attackers, midfield players, and defenders. There is a high degree of mobility and adaptability, the players changing positions according to immediate needs.