Strikeout - Rules

Rules

A pitcher receives credit for (and a batter is charged with) a strikeout on any third strike, but a batter is out only if one of the following is true:

1. The third strike is pitched and caught in flight by the catcher (including foul tips);
2. On any third strike, if a baserunner is on first and there are zero or one outs;
3. The third strike is bunted foul and is not caught by a fielder.

Thus, it is possible for a batter to strike out, but still become a runner and reach base safely if the catcher is unable to catch the third strike cleanly, and he then does not either tag out the batter or force him out at first base. In Japan, this is called furinige (振り逃げ?), or "swing and escape." In Major League Baseball, it is known as an uncaught third strike. When this happens, pitchers will occasionally be able to record four strikeouts in one half-inning.

In baseball scorekeeping, a swinging strikeout is recorded as a K, or a K-S. A strikeout looking (where the batter does not swing at a pitch that the umpire then calls strike three) is often scored with a Backwards K, and sometimes as a K-L. Despite the scorekeeping custom of using "K" for strikeout, "SO" is the official abbreviation used by Major League Baseball.

"K" is still commonly used by fans and enthusiasts for purposes other than official record-keeping. One baseball ritual involves fans attaching a succession of small "K" signs to the nearest railing, one added for every strikeout notched by the home team's pitcher. The "K" may be placed backwards in cases where the batter strikes out looking, just as it would appear on a scorecard. Virtually every televised display of a high-strikeout major league game will include a shot of a fan's strikeout display, and if the pitcher continues to strike out batters, the display may be shown following every strikeout.

The use of "K" for a strikeout was invented by Henry Chadwick, a newspaper journalist who is widely credited as the originator of the box score and the baseball scorecard. As is true in much of baseball, both the box score and scorecard remain largely unchanged to this day. Chadwick decided to use "K", the last letter in "struck", since the letter "S" was used for "sacrifice." Chadwick was responsible for several other scorekeeping conventions, including the use of numbers to designate player positions.

Those unaware of Chadwick's contributions have speculated that "K" was derived from the last name of 19th century pitcher Matt Kilroy. If not for the evidence supporting Chadwick's earlier use of "K", this explanation would be reasonable. Kilroy raised the prominence of the strikeout, setting an all-time single-season record of 513 strikeouts in 1886, only two years after overhand pitching was permitted. His record, however, is limited to its era since the pitcher's mound was only 50 feet (15 m) from the batter during that season. It was moved to its current distance of 60'6" in 1893. The modern record (1901–present) is 383 strikeouts, held by Nolan Ryan, one better than Sandy Koufax's 382.