The basic equipment or kit players are required to wear includes a shirt, shorts, socks, footwear and adequate shin guards. An athletic supporter and protective cup is highly recommended for male players by medical experts and professionals.[75][76] Headgear is not a required piece of basic equipment, but players today may choose to wear it to protect themselves from head injury. Players are forbidden to wear or use anything that is dangerous to themselves or another player, such as jewellery or watches. The goalkeeper must wear clothing that is easily distinguishable from that worn by the other players and the match officials.[77]
A number of players may be replaced by substitutes during the course of the game. The maximum number of substitutions permitted in most competitive international and domestic league games is three, though the permitted number may vary in other competitions or in friendly matches. Common reasons for a substitution include injury, tiredness, ineffectiveness, a tactical switch, or timewasting at the end of a finely poised game. In standard adult matches, a player who has been substituted may not take further part in a match.[78] IFAB recommends "that a match should not continue if there are fewer than seven players in either team." Any decision regarding points awarded for abandoned games is left to the individual football associations.[79]
A game is officiated by a referee, who has "full authority to enforce the Laws of the Game in connection with the match to which he has been appointed" (Law 5), and whose decisions are final. The referee is assisted by two assistant referees. In many high-level games there is also a fourth official who assists the referee and may replace another official should the need arise.[80]
Ball
The ball is spherical with a circumference of between 68 and 70 centimetres (27 and 28 in), a weight in the range of 410 to 450 grams (14 to 16 oz), and a pressure between 0.6 and 1.1 bars (8.5 and 15.6 pounds per square inch) at sea level. In the past the ball was made up of leather panels sewn together, with a latex bladder for pressurisation but modern balls at all levels of the game are now synthetic.[81][82]
Pitch
Standard pitch measurements (See Imperial version)
As the Laws were formulated in England, and were initially administered solely by the four British football associations within IFAB, the standard dimensions of a football pitch were originally expressed in imperial units. The Laws now express dimensions with approximate metric equivalents (followed by traditional units in brackets), though use of imperial units remains popular in English-speaking countries with a relatively recent history of metrication (or only partial metrication), such as Britain.[83]
The length of the pitch, or field, for international adult matches is in the range of 100–110 m (110–120 yd) and the width is in the range of 64–75 m (70–80 yd). Fields for non-international matches may be 90–120 m (100–130 yd) length and 45–90 m (50–100 yd) in width, provided that the pitch does not become square. In 2008, the IFAB initially approved a fixed size of 105 m (344 ft) long and 68 m (223 ft) wide as a standard pitch dimension for international matches;[84] however, this decision was later put on hold and was never actually implemented.[85]
The longer boundary lines are touchlines, while the shorter boundaries (on which the goals are placed) are goal lines. A rectangular goal is positioned at the middle of each goal line.[86] The inner edges of the vertical goal posts must be 24 feet (7.3 m) apart, and the lower edge of the horizontal crossbar supported by the goal posts must be 8 feet (2.4 m) above the ground. Nets are usually placed behind the goal, but are not required by the Laws.[87]
In front of the goal is the penalty area. This area is marked by the goal line, two lines starting on the goal line 16.5 m (18 yd) from the goalposts and extending 16.5 m (18 yd) into the pitch perpendicular to the goal line, and a line joining them. This area has a number of functions, the most prominent being to mark where the goalkeeper may handle the ball and where a penalty foul by a member of the defending team becomes punishable by a penalty kick. Other markings define the position of the ball or players at kick-offs, goal kicks, penalty kicks and corner kicks.[88]