Fungo

A baseball bat is a smooth wooden or metal club used in the sport of baseball to hit the ball after it is thrown by the pitcher. By regulation it may be no more than 2.75 inches in diameter at the thickest part and no more than 42 inches (1,100 mm) long. Although historically bats approaching 3 pounds (1.4 kg) were swung, today bats of 33 ounces (0.94 kg) are common, topping out at 34 ounces (0.96 kg) to 36 ounces (1.0 kg).

Although using a stick to hit a ball is a somewhat simple concept, the bat is a complex object. It is carved or constructed very carefully to allow a quick, balanced swing while providing power. The bat is divided into several regions. The barrel is the thick part of the bat, where it is meant to hit the ball. The part of the barrel best for hitting the ball, according to construction and swinging style, is often called the sweet spot. The end of the barrel is not part of the sweet spot and is simply called the top, end or cap of the bat. The barrel narrows and becomes the handle. The handle is very thin, so that batters can comfortably grip the bat in their hands. Sometimes, especially on metal bats, the handle is wrapped with a rubber or tape grip. Finally, below the handle is the knob of the bat, a wider piece that keeps the bat from slipping from a batter's hands. Over the decades, the bat's form has become more refined. During the 19th century, many shapes were experimented with, as well as handle designs. Today, bats are much more uniform in design.

"Lumber" is an often-used slang term for a bat, especially when wielded by a particularly able batter.

The bat drop of a bat is its weight, in ounces, minus its length, in inches. For example, a 30-ounce, 33-inch-long bat has a bat drop of minus 3 (30 − 33 = −3). Larger bat drops help to increase swing speed. Bats with smaller drops create more power.

In the mid-1800s, baseball batters were known to shape or whittle their own bats by hand. This allowed there to be a wide variety in shape, size, and weight. For example, there were flat bats, round bats, short bats, and fat bats. Earlier bats were known to be much heavier and larger than today's regulated ones.

Since the bat regulations were set, there have not been many major design changes in the bats.

In the American major leagues, Rule 1.10(a) states:

The bat shall be a smooth, round stick not more than 2.61 inches in diameter at the thickest part and not more than 42 inches in length. The bat shall be one piece of solid wood.

...
Wikipedia