Pitcher's plate

A baseball field, also called a ball field or a baseball diamond, is the field upon which the game of baseball is played. The term can also be used as a metonym for a baseball park.

The starting point for much of the action on the field is home plate, which is a five-sided slab of whitened rubber, 17 inches (43.2 cm) square with two of the corners removed so that one edge is 17 inches (43.2 cm) long, two adjacent sides are 8.5 inches (21.6 cm) and the remaining two sides are 12 inches (30.5 cm) and set at an angle to make a point. Adjacent to each of the two parallel 8.5-inch (21.6 cm) sides is a batter's box. The point of home plate where the two 12-inch (30.5 cm) sides meet at right angles is at one corner of a ninety-foot (27.5 m) square. The other three corners of the square, in counterclockwise order from home plate, are called first base, second base, and third base. Three canvas bags fifteen inches (38 cm) square mark the three bases. These three bags along with home plate form the four points at the corners of the infield.

All the bases, including home plate, lie entirely within fair territory. Thus, any batted ball that touches those bases must necessarily be in fair territory. While the first and third base bags are placed so that they lie inside the 90-foot (27.5 m) square formed by the bases, the second base bag is placed so that its center (unlike first, third and home) coincides exactly with the "point" of the ninety-foot (27.5 m) infield square. Thus, although the "points" of the bases are 90 feet (27.5 m) apart, the physical distance between each successive pair of base markers is closer to 88 feet (26.8 m).

The lines from home plate to first and third bases extend to the nearest fence, stand or other obstruction and are called the foul lines. The portion of the playing field between (and including) the foul lines is fair territory; the rest is "foul territory." The area in the vicinity of the square formed by the bases is called the infield; fair territory outside the infield is known as the outfield. Most baseball fields are enclosed with a fence that marks the outer edge of the outfield. The fence is usually set at a distance ranging from 300 to 420 feet (91 to 128 m) from home plate. Most professional and college baseball fields have a right and left foul pole. These poles are at the intersection of the foul lines and the respective ends of the outfield fence and, unless otherwise specified within the ground rules, lie in fair territory. Thus, a batted ball that passes over the outfield wall in flight and touches the foul pole is a fair ball and the batter is awarded a home run.

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Wikipedia