Baseball fans are likely familiar with the “K,” which represents a strikeout in the sport. But how did this symbol become synonymous with the third out? Invented by Henry Chadwick, the “K” was added to scorecards to represent strikeouts. This baseball pioneer, who is known as the father of baseball, was a sportswriter and statistician who also created box scores, ERA, and hitters’ batting averages. He likely chose the letter K because it was the last letter in “struck,” the word describing what happens during a strikeout. The backward K represents when the umpire calls a third strike on a hitter, who doesn’t swing, while a forward K represents a swinging strikeout.
Fans have taken up the K as well, with some creating creative signs to track the home team’s strikeouts. New York Mets fans are credited with being the first to add K’s to the stadium during the 1980s, when pitcher Dwight Gooden became known for his strikeouts. Some fans use K’s to spell out a pitcher’s name, while others place them in a tally beyond the outfield fence. In addition to being a symbol of the third out, the K also factors into statistics like K/9 (SO9) rate, which represents the number of strikeouts that a pitcher records during nine innings. Nolan Ryan holds the record for the most career strikeouts in MLB history with 5,714, while Ron Necciai and four other pitchers have struck out 27 batters in a single game.