Football or soccer is a team sport played between two teams of eleven players with a spherical ball. It is played by 250 million players in over 200 countries and dependencies, making it the worlds most popular sport. The game is played on a rectangular field with a goal at each end. The object of the game is to score by getting the ball into the opposing goal.
Players are not allowed to touch the ball with their hands or arms while it is in play, unless they are goalkeepers (and then only when within their penalty area). Other players mainly use their feet to strike or pass the ball, but may also use their head or torso. The team that scores the most goals by the end of the match wins. If the score is level at the end of the game, either a draw is declared or the game goes into extra time or a penalty shootout depending on the format of the competition.
Each team consists of a maximum of eleven players (excluding substitutes), one of whom must be the goalkeeper. Competition rules may state a minimum number of players required to constitute a team, which is usually seven. Goalkeepers are the only players allowed to play the ball with their hands or arms, provided they do so within the penalty area in front of their own goal. Though there are a variety of positions in which the outfield (non-goalkeeper) players are strategically placed by a coach, these positions are not defined or required by the Laws.
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. 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.
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. 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.
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.
A standard adult football match consists of two periods of 45 minutes each, known as halves. Each half runs continuously, meaning that the clock is not stopped when the ball is out of play. There is usually a 15-minute half-time break between halves. The end of the match is known as full-time. The referee is the official timekeeper for the match, and may make an allowance for time lost through substitutions, injured players requiring attention, or other stoppages.used as a synonym. The duration of stoppage time is at the sole discretion of the referee. The referee alone signals the end of the match. In matches where a fourth official is appointed, towards the end of the half the referee signals how many minutes of stoppage time he intends to add.