Strikeout in the context of "Out (baseball)"

Throughout the history of baseball, the rules of the game have changed frequently as the game continues to evolve. A few typical rules that 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.

In baseball, the strike zone is the area of space through which a pitch must pass in order to be called a strike even if the batter does not swing. The strike zone is defined as the volume of space above home plate and between the batter's knees and the midpoint of his torso. Whether a pitch passes through the zone is decided by an umpire, who is generally positioned behind the catcher.

Strikes are desirable for the pitcher and the fielding team, as three strikes result in a strikeout of that batter. A pitch that misses the strike zone is called a ball if the batter does not swing at it. Balls are desirable for the batter and the batting team, as four balls allow the batter to take a "walk" to first base as a base on balls.

In baseball, a player is credited with a plate appearance (denoted by PA) each time he completes a turn batting. Under Rule 5.04(c) of the Official Baseball Rules, a player completes a turn batting when he is put out or becomes a runner. This happens when he strikes out or is declared out before reaching first base; or when he reaches first base safely or is awarded first base (by a base on balls, hit by pitch, catcher's interference, or obstruction); or when he hits a fair ball which causes a preceding runner to be put out for the third out before he himself is put out or reaches first base safely (see also left on base, fielder's choice, force play). A very similar baseball statistic, at bats, counts a subset of plate appearances that end under certain circumstances.

In baseball statistics, a putout (PO) is awarded to a defensive player who (generally while in secure possession of the ball) records an out by one of the following methods:

• Tagging a runner with the ball when the runner is not touching a base (a tagout)
• Catching a batted ball on the fly (a flyout)
• Retrieving a batted ball hit along the ground which a defensive player subsequently throws to another defensive player who then catches it- the latter simultaneously occupying a base, or by subsequently touching a base while in possession of the ball- thus recording an out of a batter or runner, before the batter, or non-batting runner, can touch the base to which he is compelled to advance (a force out- referred to as a groundout if the player who has been put out is the batter-runner attempting to reach first base- or, if done after a flyout, a doubling off).
• Catching a thrown ball and tagging a base to record an out on an appeal play
• Catching a third strike (a strikeout)
• Being positioned closest to a runner called out for interference

In a regulation nine-inning game, the winning team will always have a total of 27 putouts, as one putout is awarded for every defensive out made; this is one aspect of proving a box score.