Baseball is played by two teams of nine players each, and a game is divided into nine innings. In September 1845, the New York Knickerbocker club published a formal set of baseball rules. The game has grown since then, and some of its rules have odd names. Here are the ones that make new fans stop and ask what they mean.

Start with the count. The strike zone is the area over home plate between the middle of the batter's body and the kneecaps. A pitch outside it that the batter does not swing at is a ball. A batter who gets four balls walks to first base. Umpires enforce the rules and decide whether a pitch is a strike or a ball.

Then there is the foul ball. Fair territory is the part of the field inside the first-base and third-base lines. A foul ball counts as a strike, unless the batter already has two strikes. Three strikes make a strikeout. A batter is also out if the ball is caught or thrown to first base before the batter gets there.

The infield fly rule is one of the odd ones. It 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. A double play is a play in which two runners or batters are put out.

Pitchers have rules to follow, too. A balk is an illegal motion by the pitcher with runners on base, and every runner moves up one base. The pitcher stands on the pitcher's mound, in the middle of the infield. The catcher crouches behind home plate and catches the pitches.

The numbers behind pitching are big. Earned run average (ERA) is the number of earned runs a pitcher allows per nine innings. Nolan Ryan struck out 5,714 batters, and as of November 2026 that is the most in major league history. Cy Young won 511 games as a pitcher, almost 100 more than any other pitcher in history, as of November 2026.

Running has its records too. A stolen base happens when a runner moves up to the next base on his own, not because of a hit. Rickey Henderson stole 1,406 bases in his career, the most in major league history as of November 2026. Home runs have big totals as well. Babe Ruth hit 714 home runs in his major league career. Hank Aaron finished his career with 755.

Baseball is a game for kids, too. The first official Little League game was played on June 6, 1939. Young pitchers should learn the fastball first and add a changeup once skilled. MLB's Pitch Smart advises players aged 9 to 12 to throw only fastballs and changeups.

Words to know

• Knickerbocker: an early club
• infield: inside the diamond
• balk: an illegal motion
• changeup: slower pitch
• occupied: with a runner