Baseballisabat-and-ballsportplayedbetweentwoteamsofnineplayerseach.Thegoalistoscorerunsbyhittingathrownballwithabatandtouchingaseriesoffourbasesarrangedatthecornersofaninety-footsquare,ordiamond.Playersononeteam(thebattingteam)taketurnshittingagainstthepitcheroftheotherteam(thefieldingteam),whichtriestostopthemfromscoringrunsbygettinghittersoutinanyofseveralways.Aplayeronthebattingteamcanstopatanyofthebasesandlateradvanceviaateammate'shitorothermeans.Theteamsswitchbetweenbattingandfieldingwheneverthefieldingteamrecordsthreeouts.Oneturnatbatforeachteamconstitutesaninning;nineinningsmakeupaprofessionalgame.Theteamwiththemostrunsattheendofthegamewins.

　　Evolvingfromolderbat-and-ballgames,anearlyformofbaseballwasbeingplayedinEnglandbythemid-eighteenthcentury.ThisgameandtherelatedrounderswerebroughtbyBritishandIrishimmigrantstoNorthAmerica,wherethemodernversionofbaseballdeveloped.Bythelatenineteenthcentury,baseballwaswidelyrecognizedasthenationalsportoftheUnitedStates.Baseballontheprofessional,amateur,andyouthlevelsisnowpopularinNorthAmerica,partsofCentralandSouthAmericaandtheCaribbean,andpartsofEastAsia.Thegameissometimesreferredtoashardball,incontrasttothederivativegameofsoftball.

　　InNorthAmerica,professionalMajorLeagueBaseball(MLB)teamsaredividedintotheNationalLeague(NL)andAmericanLeague(AL).Eachleaguehasthreedivisions:East,West,andCentral.Everyyear,thechampionofMajorLeagueBaseballisdeterminedbyplayoffsthatculminateintheWorldSeries.Fourteamsmaketheplayoffsfromeachleague:thethreeregularseasondivisionwinners,plusonewildcardteam.BaseballistheleadingteamsportinbothJapanandCuba,andthetoplevelofplayissimilarlysplitbetweentwoleagues:Japan'sCentralLeagueandPacificLeague;Cuba'sWestLeagueandEastLeague.IntheNationalandCentralleagues,thepitcherisrequiredtobat,perthetraditionalrules.IntheAmerican,Pacific,andbothCubanleagues,thereisatenthplayer,adesignatedhitter,whobatsforthepitcher.Eachtop-levelteamhasafarmsystemofoneormoreminorleagueteams.Theseteamsallowyoungerplayerstodevelopastheygainon-fieldexperienceagainstopponentswithsimilarlevelsofskill.