Baseball rules

Throughout baseball's history, the rules have frequently changed as the game continues to evolve. A few typical rules most professional leagues have in common are that four balls are a base on balls, three strikes are a strikeout, and three outs end a half-inning.

Baseball evolved out of bat-and-ball games in the mid-19th century, and its modern rules are based mainly on those first published in 1848. Most rule sets are generally based on the Official Baseball Rules (OBR) published by Major League Baseball (MLB), though various minor variations exist from league to league; the World Baseball Softball Confederation maintains its own official rule set for international competition.