A domino is a small tile that represents the result of rolling two dice. Each domino has an arrangement of dots, or “pips,” on one side and is blank on the other. The most common domino set has 28 unique tiles, each with pips from zero to six. A domino is typically about 2 inches long, 1 inch wide, and 3/8 inch thick – small enough to be held comfortably in the hand but large enough to be easily manipulated and able to stand on edge.

Dominoes are used in a wide variety of games, both simple and complex. They are also a component in many mechanical devices, including Rube Goldberg machines. Dominoes are often arranged in artistic designs, such as a line of squares that form a picture or the sides of a pyramid or a castle.

Most domino games are played on a tabletop, and the pieces are set up in a line so that they touch each other at their exposed ends. Each player then plays a domino by positioning it onto the line so that its matching end touches the end of another domino in the chain (one’s touching one’s, two’s touching two’s, etc.). Each player scores points as the chain of matched ends increases in length.

Players draw their tiles from a bag or container and place them on the edge of the table in front of them. The first player to do so, either by drawing lots or by having the heaviest hand, places a domino on the table. The next player then takes his turn. He must play a domino so that its matching end touches the end of an existing domino in the chain (one’s touched one’s, two’s touched two’s, or three’s touched three’s). If it is a double, it is placed cross-ways on the edge of the other domino. The resulting domino chain develops into a snake-like shape that runs around the table.

While most dominoes are made of plastic, they can be made of a variety of materials. The more traditional European sets are made of bone, silver lip ocean pearl oyster shell (mother of pearl), ivory, or dark hardwood such as ebony with contrasting black or white pips. Other natural materials such as stone (e.g., marble or granite) have been used to make dominoes. Similarly, metals such as brass and pewter have been used to make them. Some sets are also available in ceramic clay or even frosted glass or crystal.

While there are several different types of dominoes, the most commonly used ones are the double-twelve and double-nine sets. These have 91 and 55 dominoes respectively and can be played with four or more players. Larger sets such as the double-21 are possible but not commonly sold, since identifying the pips on a domino becomes difficult at this point and a double-21 set would have far more dominoes than is needed for most games.