A domino is a small rectangular block, marked on one face with an arrangement of spots resembling those on dice. A domino set consists of these blocks, and they are used to play a variety of games. The word domino derives from the Latin dominium, meaning “flip over.” Unlike playing cards or dice, which have specific rules and uses, the basic principles of domino are general enough to allow for many variations.

When a domino is positioned upright, it stores potential energy. This energy is derived from its position and the force of gravity. As the domino falls, much of this energy is converted to kinetic energy, or the energy of motion, which travels from one domino to the next in a chain reaction.

In a game of domino, players take turns placing one domino edge to edge against another, such that the adjacent faces are either identical or form some specified total (such as a number of points or a number of lines). In most Western domino games, a player places a domino only if the current position of the other dominos allows for it. If a player cannot place a domino, she must draw from the sleeping dominos until she can.

Most dominoes are made of wood or plastic, although sets have also been produced from stone, other natural materials, metals, and ceramic clay. The most common material, though, is polymer resin. This type of plastic is available in a wide variety of colors and finishes, and it has the advantage of being relatively inexpensive compared with other materials.

The most familiar domino games are blocking and scoring ones, such as Block and Draw. In these, each domino is placed so that it touches a matching end of the other tiles already on the table. The chain of matches grows in length until a player cannot place any more dominos and passes the turn to his or her opponent. Most large domino sets feature a numbering system that makes it possible to identify the value of each piece from its pips, or markings.

Dominos are most often used to play positional games, but they are also sometimes played as a sort of abstract puzzle. Some people use dominos to explore how a system or process works, or even to test their own creativity. For example, in a game called The Domino Effect, a person writes down his or her goal and then checks whether it is likely to be achieved by using dominoes to represent the steps needed to reach that goal.

In more esoteric applications, dominoes have been used to illustrate the power of influence and persuasion, as well as the limitations of human reasoning and decision making. They are often used as a tool to help students learn about systems and processes, and to develop their ability to identify and evaluate patterns. Dominos are also popular in art and architecture, as they can be manipulated to create shapes, structures, and compositions that might not otherwise be feasible with more traditional building materials.