Baseball is a bat-and-ball sport played between two teams of nine players each, taking turns batting and fielding. Gameplay centers around the pitcher on the fielding team throwing a baseball to a batter on the opposing team, who tries to hit it into the field of play. Successfully batted balls allow players on the batting team to advance around a circuit of four bases and score runs. Meanwhile, the fielding team attempts to "put out" the batters and baserunners, removing them from play and preventing them from scoring. Once the fielding team records three outs, the offensive and defensive sides switch roles. Play continues until a defined number of innings have been completed, whereupon the team with the most runs wins.
Baseball evolved from older bat-and-ball games that gained popularity in England during the mid-18th century. Immigrants brought these games to North America, where modern baseball developed into organized clubs playing under codified rules by the mid-19th century. Baseball's American origins, as well as its reputation as a source of escapism during troubled points in American history such as the American Civil War and the Great Depression, have led the sport to receive the moniker of "America's Pastime". Since the late 19th century, it has been unofficially recognized as the national sport of the United States, though in modern times is less popular than some other sports. In addition to North America, baseball spread throughout the rest of the Americas and the Asia–Pacific in the 19th and 20th centuries, and is now among the most popular sports in parts of Central and South America, the Caribbean, and East Asia, particularly in Japan, South Korea, and Taiwan.
In Major League Baseball (MLB), the highest level of professional baseball in the United States and Canada, teams are divided into the National League (NL) and American League (AL), each with three divisions: East, West, and Central. The MLB champion is determined by playoffs that culminate in the World Series. The top level of play is similarly split in Japan between the Central and Pacific Leagues and in Cuba between the West League and East League. The World Baseball Classic, organized by the World Baseball Softball Confederation, is the major international competition of the sport and attracts the top national teams from around the world. Baseball was played at the Olympic Games from 1992 to 2008 and in 2020, and will return in 2028.
A baseball game is played between two teams, each composed of nine players, that take turns playing offense (batting and baserunning) and defense (pitching and fielding). A pair of turns, one at bat and one in the field, by each team constitutes an inning. A game consists of nine innings (seven innings at the high school level and in doubleheaders in college and Minor League Baseball; and six innings at the Little League level). One team—customarily the visiting team—bats in the top, or first half, of every inning. The other team—customarily the home team—bats in the bottom, or second half, of every inning.
The goal of the game is to score more points (runs) than the other team. The players on the team at bat attempt to score runs by touching all four bases, in order, set at the corners of the square-shaped baseball diamond. A player bats at home plate and must attempt to safely reach a base before proceeding, counterclockwise, from first base, to second base, third base, and back home to score a run. The team in the field attempts to prevent runs from scoring by recording outs, which remove opposing players from offensive action until their next turn at bat comes up again. When three outs are recorded, the teams switch roles for the next half-inning. If the score of the game is tied after nine innings, extra innings are played to resolve the contest. Many amateur games, particularly unorganized ones, involve different numbers of players and innings.
The game is played on a field whose primary boundaries, the foul lines, extend forward from home plate at 45-degree angles. The 90-degree area within the foul lines is referred to as fair territory; the 270-degree area outside them is foul territory. The part of the field enclosed by the bases and several yards beyond them is the infield; the area farther beyond the infield is the outfield. In the middle of the infield is a raised pitcher's mound, with a rectangular rubber plate (the rubber) at its center. The outer boundary of the outfield is typically demarcated by a raised fence, which may be of any material and height. The fair territory between home plate and the outfield boundary is baseball's field of play, though significant events can take place in foul territory, as well.
There are three basic tools of baseball: the ball, the bat, and the glove or mitt:
The baseball is about the size of an adult's fist, around 9 inches (23 centimeters) in circumference. It has a rubber or cork center, wound in yarn and covered in white cowhide, with red stitching.
The bat is a hitting tool, traditionally made of a single, solid piece of wood. Other materials are now commonly used for nonprofessional games. It is a hard round stick, about 2.5 inches (6.4 centimeters) in diameter at the hitting end, tapering to a narrower handle and culminating in a knob. Bats used by adults are typically around 34 inches (86 centimeters) long, and not longer than 42 inches (110 centimeters).
The glove or mitt is a fielding tool, made of padded leather with webbing between the fingers. As an aid in catching and holding onto the ball, it takes various shapes to meet the specific needs of different fielding positions.
Protective helmets are also standard equipment for all batters.
At the beginning of each half-inning, the nine players of the fielding team arrange themselves around the field. One of them, the pitcher, stands on the pitcher's mound. The pitcher begins the pitching delivery with one foot on the rubber, pushing off it to gain velocity when throwing toward home plate. Another fielding team player, the catcher, squats on the far side of home plate, facing the pitcher. The rest of the fielding team faces home plate, typically arranged as four infielders—who set up along or within a few yards outside the imaginary lines (basepaths) between first, second, and third base—and three outfielders. In the standard arrangement, there is a first baseman positioned several steps to the left of first base, a second baseman to the right of second base, a shortstop to the left of second base, and a third baseman to the right of third base. The basic outfield positions are left fielder, center fielder, and right fielder. With the exception of the catcher, all fielders are required to be in fair territory when the pitch is delivered. A neutral umpire sets up behind the catcher. Other umpires will be distributed around the field as well.
Play starts with a member of the batting team, the batter, standing in either of the two batter's boxes next to home plate, holding a bat. The batter waits for the pitcher to throw a pitch (the ball) toward home plate, and attempts to hit the ball with the bat. The catcher catches pitches that the batter does not hit—as a result of either electing not to swing or failing to connect—and returns them to the pitcher. A batter who hits the ball into the field of play must drop the bat and begin running toward first base, at which point the player is referred to as a runner (or, until the play is over, a batter-runner).
A batter-runner who reaches first base without being put out is said to be safe and is on base. A batter-runner may choose to remain at first base or attempt to advance to second base or even beyond—however far the player believes can be reached safely. A player who reaches base despite proper play by the fielders has recorded a hit. A player who reaches first base safely on a hit is credited with a single. If a player makes it to second base safely as a direct result of a hit, it is a double; third base, a triple. If the ball is hit in the air within the foul lines over the entire outfield (and outfield fence, if there is one), or if the batter-runner otherwise safely circles all the bases, it is a home run: the batter and any runners on base may all freely circle the bases, each scoring a run. This is the most desirable result for the batter. The ultimate and most desirable result possible for a batter would be to hit a home run while all three bases are occupied or "loaded", thus scoring four runs on a single hit. This is called a grand slam. A player who reaches base due to a fielding mistake is not credited with a hit—instead, the responsible fielder is charged with an error.