The basic rules of baseball govern how teams bat, field, score runs and record outs. Two teams alternate between offence and defence, with the offensive team attempting to score and the defensive team attempting to prevent scoring. The batting team sends players to home plate according to its batting order, while the defensive team places its players around the field and has a pitcher deliver the ball.
The batter attempts to hit a legally pitched ball into fair territory and then advance around the bases. The defensive team attempts to record three outs. When three outs are recorded, the teams exchange roles. This alternating process continues through the innings specified by the competition rules. The team with more runs at the end wins, subject to competition specific provisions concerning tied games, extra innings and other circumstances. The basic structure is therefore built around pitches, plate appearances, outs, bases, runs and alternating offensive and defensive turns.
A batter faces a count consisting of balls and strikes. A called or swinging strike counts as one strike, while a pitch outside the strike zone that the batter does not swing at is generally called a ball. Three strikes normally result in a strikeout and an out, subject to specific rules concerning foul balls, foul tips and dropped third strikes. Four balls normally result in a walk, giving the batter first base.
The strike zone is a defined three dimensional area over home plate, with its vertical boundaries determined by the batter's stance and the relevant rule definition. The umpire determines whether pitches meet the criteria for called balls and strikes. A batter can also put the ball into play by making fair contact. The count is strategically important because it changes the relationship between pitching options and hitting expectations.
A run is scored when a runner legally advances around the bases and touches home plate after touching the other bases in the required sequence. Runners normally advance from first to second, second to third and third to home. A batter who hits a home run can ordinarily touch all four bases and score, while existing runners can also score.
Runs can arise through hits, walks combined with later advancement, errors, sacrifice plays, wild pitches, passed balls and other legal events. The defensive team's objective is to prevent runners from completing this sequence. A runner can be retired by being tagged while off a base, by a force out involving a base that the runner is required to advance to, or by other specified forms of out. Base running therefore involves both physical speed and knowledge of the rules governing force situations, tagging and advancement.
Three outs normally complete one team's offensive half inning. An inning therefore contains two halves, with each team batting once. In a standard nine inning game, nine innings provide each team with up to nine offensive half innings, although the home team may not need to bat in the bottom of the ninth if it is already ahead. If the score is tied after the scheduled innings, extra innings may be played under the rules of the relevant competition.
The exact treatment of extra innings, including runner placement or other special provisions, varies by league and level. The number of innings also varies in some forms of baseball. Professional games commonly use nine innings, while certain youth, amateur and doubleheader formats may use fewer. The inning system is therefore a basic rule framework but not an identical fixed structure across every baseball competition.
Fair and foul territory is another fundamental part of the rules. A batted ball is generally fair if it first contacts the ground or a fielder in the prescribed fair territory, subject to detailed rule definitions. A ball that travels into foul territory can be called a foul ball. A foul ball normally counts as a strike when the batter has fewer than two strikes, but a standard foul ball does not ordinarily produce a third strike.
There are exceptions, including situations involving bunts and foul tips. A foul ball that is caught before touching the ground can result in an out. The fair or foul status of a ball can therefore influence whether runners may advance, whether the batter remains in the plate appearance and whether an out is recorded.
Defensive players can record outs through several mechanisms. A fly ball or line drive caught before touching the ground normally produces an out on the batter. A force out occurs when a runner is required to advance because the batter becomes a runner and the fielder legally touches the relevant base while possessing the ball.
A tag out occurs when a defensive player touches a runner with the ball or a glove containing the ball while the runner is not protected by a base, subject to the rules. Strikeouts are another common form of out and result directly from the batter's failure to complete the plate appearance without accumulating three strikes. These mechanisms require precise rule application because whether a runner is forced, whether a tag is valid and whether a catch has been completed can depend on the exact circumstances.
The batting order is also governed by rules. Players generally must bat in the established order, and a team can be penalised for batting out of order under the applicable rules. Defensive substitutions can change which players occupy positions, and designated hitter rules can allow a player to bat without playing a defensive position, although the exact implementation varies between competitions. Pitchers are subject to specific substitution and eligibility rules, while defensive players can also be replaced.
The rules therefore regulate not only what happens during a pitch but also the composition of the team and the sequence in which players participate. Coaches and managers must understand these procedural rules because an otherwise successful tactical decision can produce a disadvantage if it violates substitution or batting order requirements.
The basic rules are designed to create a contest in which scoring opportunities arise from controlled interactions between batting and fielding. They establish what constitutes a legal pitch, strike, ball, fair ball, foul ball, hit, out, base advancement and run. More detailed rules govern interference, obstruction, balks, pitching procedures, runner behaviour, substitutions, equipment, timing, appeals and umpire decisions.
Different governing bodies can have variations, so the rules of Major League Baseball are not necessarily identical to those used in international, amateur, youth or recreational baseball. Nevertheless, the central framework remains consistent: one team bats while the other fields, the offence attempts to advance runners and score, the defence attempts to record three outs, and the teams alternate roles until the game is completed.
