Baseball is a contest between the pitcher and the batter, and some rule changes have helped one side. In 1893 the distance from the pitcher to the batter was lengthened from 55 feet 6 inches to 60 feet 6 inches, which helped the hitters. After 1968, nicknamed the "Year of the Pitcher," baseball lowered the pitcher's mound from 15 inches to 10 inches and shrank the strike zone, the area over home plate between the middle of the batter's body and the kneecaps. The strike zone has changed several times in baseball history, and the current version has been used since 1996, as of November 2026.

Follow one pitch. The pitching rubber is 60 feet, 6 inches from home plate, and the pitch must cross the strike zone. A pitched baseball loses about 10 percent of its speed on the way to the plate: a pitch that leaves the hand at 95 mph crosses the plate at about 86 mph.

Then comes the swing. Exit velocity is the speed of the baseball as it comes off the bat right after contact; a faster ball gives the defense less time to react. Launch angle is the vertical angle at which the ball leaves the bat: under 10 degrees is a ground ball, 10 to 25 a line drive, 25 to 50 a fly ball and over 50 a pop up. Air drag takes a lot of distance off a long fly ball: one that carries 400 feet would carry about 700 feet if there were no drag.

Statistics try to measure all of this. Batting average is a batter's hits divided by his times at bat, and slugging percentage is total bases per at-bat: (singles + 2 x doubles + 3 x triples + 4 x home runs) divided by at-bats. On-base percentage was invented in the 1940s-50s by Dodgers executive Branch Rickey and statistician Allan Roth, and did not become an official statistic until 1984. The save was first defined with specific rules by writer Jerome Holtzman in the early 1960s and became an official statistic in 1969. Earned run average (ERA) is the number of earned runs a pitcher allows per nine innings.

Rules about fairness need judges. The infield fly rule applies to a fair fly ball that an infielder can catch with ordinary effort when first and second base, or all three bases, are occupied before the second out. It protects the runners: without it, a team could let a shallow fly ball drop on purpose to force out runners who had stayed put. Umpires enforce the rules and decide whether a runner is safe or out and whether a pitch is a strike or a ball. As of November 2026, Major League replay reviews are made at a Replay Command Center in New York by replay officials, who are full-time Major League umpires.

Some players pushed the numbers far. In 1980 Rickey Henderson broke Ty Cobb's 65-year-old American League record of 96 stolen bases with 100, and in 1982 he stole 130 bases. He stole 1,406 bases in his career, the most in major league history as of November 2026.

Words to know

• contest: a match
• velocity: speed
• drag: air resistance
• percentage: a share
• occupied: holding runners