Section 4: Players & Officials
Number of Players (Law 3, Section 1). A match is played by two teams of a maximum of five players each, one of whom must be the goalkeeper. A match may not start or resume if either team has fewer than three players.
Substitutions (Law 3, Section 2). An unlimited number of substitutions may be made during a match, at any time, whether the ball is in play or not. In official competitions organised under the auspices of FIFA, confederations or member associations, a maximum of seven substitutes may be used; in unofficial national "A" team matches, up to ten; in all other matches, a higher number is allowed only by agreement of both teams and notice to the referees.
Substitution Procedure (Law 3, Section 4). Substitutions occur through the substitution zone: the player being replaced leaves via the zone without needing referee permission, and the substitute may enter only after that player has left. The substitution is complete once the substitute fully enters the pitch through the zone.
Team Captain (Law 3, Section 14). Each team must name a captain who wears an identifying armband; the captain carries a degree of responsibility for the team's conduct but no special privileges under the Laws.
The Referees (Law 5). Matches are controlled by two referees with equal authority, whose decisions on facts connected with play are final. Referees have full authority to enforce the Laws from their pre-match pitch inspection until they leave the pitch after the match, including any penalty shoot-out.
Other Match Officials (Law 6). Matches are supported by assistant referees and, in official competitions, a fourth referee; international matches under FIFA/confederation auspices additionally use a Time Review System (TRS) and, where available, video support to assist the referees' decision-making.