Association football

===Players, equipment, and officials===
{{See also|Association football positions|Formation (association football)|Substitute (association football)|Kit (association football)}}
[[File:Howard Webb3.jpg|thumb|upright=1.0|The [[referee (association football)|referee]] officiates in a football match|alt=]]
Each team consists of a maximum of eleven players (excluding [[substitute (association football)|substitutes]]), one of whom must be the [[goalkeeper (football)|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 [[association football positions|positions]] in which the outfield (non-goalkeeper) players are [[sports strategy|strategically]] placed by a coach, these positions are not defined or required by the Laws.<ref name=LAW301/>

The basic equipment or ''[[Kit (association football)|kit]]'' players are required to wear includes a shirt, shorts, socks, footwear and adequate [[shin guard]]s. An [[jockstrap|athletic supporter]] and protective cup is highly recommended for male players by medical experts and professionals.<ref>{{cite web |url=http://strikingeagles.tripod.com/health_advice_for_boys.htm |title=Health Advice for Boys |publisher=Strikingeagles.tripod.com |access-date=24 September 2013 |archive-date=27 September 2013 |archive-url=https://web.archive.org/web/20130927075108/http://strikingeagles.tripod.com/health_advice_for_boys.htm |url-status=live }}</ref><ref>{{cite web |url=http://files.leagueathletics.com/Images/Club/6097/The%20Prevention%20of%20injuries.pdf |title=Soccer Position Paper |access-date=24 September 2013 |archive-date=28 September 2013 |archive-url=https://web.archive.org/web/20130928003421/http://files.leagueathletics.com/Images/Club/6097/The%20Prevention%20of%20injuries.pdf |url-status=live }}</ref> [[Association football headgear|Headgear]] is not a required piece of basic equipment, but players today may choose to wear it to protect themselves from head injury.<ref>{{cite news|title=Football's biggest headache|url=http://www.marca.com/en/football/international-football/2017/03/12/58c54bab268e3e64368b45a8.html|access-date=17 May 2018|work=Marca|location=Spain|date=12 March 2017|archive-date=17 May 2018|archive-url=https://web.archive.org/web/20180517223832/http://www.marca.com/en/football/international-football/2017/03/12/58c54bab268e3e64368b45a8.html|url-status=live}}</ref> 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.<ref>{{cite web|url=https://www.fifa.com/flash/lotg/football/en/Laws4_01.htm |publisher=FIFA |title=Laws of the game (Law 4–Players' Equipment) |access-date=24 September 2007 |archive-url=https://web.archive.org/web/20070913141601/http://fifa.com/flash/lotg/football/en/Laws4_01.htm |archive-date=13 September 2007 |url-status=dead }}</ref>

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 five in 90 minutes,<ref>{{Cite web |date=2022-06-13 |title=Five substitutions permitted in all top-level competitions from 2022/23 |url=https://www.90min.com/posts/five-substitutions-permitted-in-all-top-level-competitions-from-2022-23 |access-date=2023-01-13 |website=90min.com |language=en-GB |archive-date=13 January 2023 |archive-url=https://web.archive.org/web/20230113223015/https://www.90min.com/posts/five-substitutions-permitted-in-all-top-level-competitions-from-2022-23 |url-status=live }}</ref> with each team being allowed one more if the game should go into extra-time; 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.<ref>{{cite web |url=https://www.fifa.com/flash/lotg/football/en/Laws3_02.htm |publisher=FIFA |title=Laws of the game (Law 3–Substitution procedure) |access-date=24 September 2007|url-status=dead |archive-url=https://web.archive.org/web/20071011144947/http://fifa.com/flash/lotg/football/en/Laws3_02.htm|archive-date=11 October 2007}}</ref> 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.<ref>{{cite book |title=Laws of the Game 2010/2011 |chapter=Law 3&nbsp;– The Number of Players |chapter-url=https://www.fifa.com/mm/document/affederation/generic/81/42/36/lawsofthegame_2010_11_e.pdf |publisher=FIFA |access-date=4 March 2011 |page=62 |archive-date=4 July 2010 |archive-url=https://web.archive.org/web/20100704211500/https://www.fifa.com/mm/document/affederation/generic/81/42/36/lawsofthegame_2010_11_e.pdf |url-status=dead }}</ref>

{{anchor|Match officials}}
A game is officiated by a [[referee (association football)|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 referee (association football)|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.<ref>{{cite web|url=https://www.fifa.com/flash/lotg/football/en/Laws5_01.htm |publisher=FIFA |title=Laws of the game (Law 5 – The referee) |access-date=24 September 2007 |archive-url=https://web.archive.org/web/20070913141909/http://fifa.com/flash/lotg/football/en/Laws5_01.htm |archive-date=13 September 2007 |url-status=dead }}</ref>

[[Goal line technology]] is used to measure if the whole ball has crossed the goal-line thereby determining whether a goal has been scored or not; this was brought in to prevent controversy. [[Video assistant referee]]s (VAR) have also been increasingly introduced in high-level matches to assist officials through video replays to correct clear and obvious mistakes. There are four types of calls that can be reviewed: mistaken identity in awarding a red or yellow card, goals and whether there was a violation during the buildup, direct red card decisions, and penalty decisions.<ref name="protocol">{{cite web |url=http://www.knvb.nl/downloads/bestand/9844/var-handbook-summary |title=Video Assistant Referees (VARs) Experiment – Protocol (Summary) |publisher=International Football Association Board |date=26 April 2017 |access-date=26 April 2017 |format=PDF |archive-url=https://web.archive.org/web/20170427192145/http://www.knvb.nl/downloads/bestand/9844/var-handbook-summary |archive-date=27 April 2017 |url-status=dead }}</ref>