Baseball is a bat and ball team sport in which two teams take turns batting and fielding, with the batting team attempting to score runs and the fielding team attempting to prevent those runs. The central contest involves a batter trying to hit a pitched baseball into the field and then advance around four bases arranged in a diamond, while the defensive team attempts to record outs before runners can score.
A run is scored when a runner legally touches first base, second base, third base and home plate in sequence. Unlike many continuous invasion sports, baseball is organised around discrete pitches, plate appearances, outs, bases and innings rather than a continuously running clock. The sport combines individual confrontations, particularly between a pitcher and batter, with coordinated team defence and baserunning. Every pitch can change the tactical situation because the result can produce a strike, ball, foul ball, hit, out, baserunner or run. Baseball therefore combines repeated short periods of highly specialised action with strategic decisions extending across an entire game.
Baseball is normally played between two teams of nine players in standard professional and adult versions, although playing formats can differ by competition and age group. The defensive team positions players around the field, including a pitcher and catcher in the central battery, four infielders and three outfielders in the traditional arrangement. The offensive team sends its batters to home plate according to a batting order.
The pitcher delivers the ball towards the catcher through the area above home plate known as the strike zone, and the batter decides whether and how to swing. After hitting the ball, the batter can become a runner and attempt to advance around the bases.
The defence can record outs by catching a batted ball before it touches the ground, tagging a runner, touching a base while holding the ball when a force play applies, or using other rule defined methods. Three outs normally end a team's offensive half inning, after which the teams exchange offensive and defensive roles.
The field is divided conceptually into the infield and outfield. The infield contains home plate, first base, second base and third base, forming the diamond through which runners advance. The outfield extends beyond the infield and is normally divided into left field, centre field and right field. The pitcher works from a raised mound located near the centre of the diamond, while the catcher occupies the area behind home plate.
The batter stands in one of two batter's boxes alongside home plate. The physical dimensions of fields can vary, particularly at different levels and between ballparks, although the bases and pitching areas are governed by playing rules. The layout creates the distinctive geometry of baseball. A ball hit to different areas can produce very different defensive possibilities, and the distance between bases influences running speed, throwing requirements and tactical decisions.
The fundamental objective for the offence is to score more runs than the opposing team. A batter generally begins with no balls and no strikes and faces pitches until the plate appearance produces an outcome such as a hit, walk, strikeout, sacrifice situation, hit by pitch or another result specified by the rules. A batter who reaches base can attempt to advance, either because of subsequent hits, walks, defensive actions or intentional baserunning.
The defence seeks three outs while preventing runners from progressing. Baseball therefore has two simultaneous strategic objectives that sometimes conflict. The offence must maximise opportunities to reach and advance while the defence must manage the probability of allowing baserunners and runs. Managers and coaches make decisions involving pitching changes, defensive positioning, substitutions, baserunning, batting order and tactical use of available players.
Baseball developed from earlier bat and ball games played in Britain and North America, with the modern form developing substantially in the nineteenth century. The exact origins are historically complex because no single moment represents the invention of the entire modern sport. Earlier games including rounders and other bat and ball traditions contributed concepts that eventually appeared in organised baseball. During the nineteenth century, clubs and governing organisations increasingly formalised rules concerning bases, innings, pitching and scoring.
Professional baseball subsequently developed in North America, particularly in the United States, where Major League Baseball became the best known professional competition. Baseball also became established in countries and regions including Japan, Cuba, the Dominican Republic, Venezuela, South Korea, Mexico, Canada and several other nations. Different historical periods produced changes to equipment, tactics, rules, professional organisation and statistical analysis.
Baseball has distinctive terminology that reflects its specialised structure. A batter becomes a runner when legally entitled to advance, a pitcher delivers pitches, a catcher receives them, and an umpire administers and interprets the rules. A plate appearance describes a batter's completed turn at the plate under statistical conventions, while an at bat is a narrower statistical category with specific exclusions.
A hit is a batted ball that allows the batter to reach base safely under scoring rules, while a home run normally allows the batter and any existing runners to score. A walk occurs when a batter receives four pitches called balls, while a strikeout occurs when the batter accumulates three strikes under the applicable rules. These terms are not interchangeable. Understanding the terminology is essential because baseball statistics and tactical discussions depend heavily on precise distinctions between outcomes.
Baseball is both an individual and collective sport. The pitcher and batter engage in a highly specialised confrontation, but every pitch also involves the catcher, defensive positioning, baserunners, coaches and other fielders. A batter may succeed individually by reaching base, yet the value of that action depends partly on the game situation. A defensive player may make an apparently routine play that becomes strategically important because it prevents a runner from advancing.
Pitch selection, defensive positioning and baserunning decisions are influenced by the count, number of outs, runners on base, score, inning, batter characteristics and pitcher characteristics. Modern baseball also makes extensive use of statistical analysis. Measures such as batting average, on base percentage, slugging percentage, earned run average, strikeout rate and walk rate describe different aspects of performance. More advanced analysis uses pitch velocity, movement, launch angle, exit velocity and defensive positioning to evaluate performance.
Baseball differs fundamentally from sports that use a continuously running game clock. A team does not normally win because it controls possession for a certain proportion of elapsed time. Instead, opportunities are divided into offensive half innings, and the number of outs controls when possession changes. This structure creates strategic situations that can be evaluated according to probability, score and remaining opportunities.
A team trailing late in a game may approach baserunning, batting and pitching differently from a team protecting a lead. The sport also permits a large number of specialised roles, particularly at advanced levels, including starting pitchers, relief pitchers, designated hitters, defensive replacements and specialist baserunners. Baseball's combination of fixed objectives, repeated pitch level decisions, specialised positions and cumulative scoring makes it distinct from many other team sports.
