A domino is a small rectangular wood or plastic block, usually marked on one face with an arrangement of dots resembling those on dice. The other face is blank or patterned identically to the markings. Dominoes are used in a variety of games to build lines or rows of tiles called a chain. Whether played by one or many players, the chains can develop elaborate and complicated patterns. Dominoes are also used as educational aids to demonstrate the principles of probability and mathematical operations.

A set of dominoes, referred to collectively as the domino game or dominoes, is the basic equipment needed for the majority of the most popular games. Although there are numerous variations of the game, nearly all of them involve laying down a row of dominoes in order to achieve a particular outcome. The simplest of these are the number games, in which a player places a domino whose value is equal to or greater than the sum total of all the other dominoes on the table.

In most cases, the first domino placed in a line of play must be a double, unless the rules state otherwise. In addition, most games require that the domino be played on either end of a line of play, and that it be joined to a tile already in place if it matches that tile’s pips in number and direction. The resulting line of play is known as the domino chain, and its structure forms part of the strategy of the game.

While the vast majority of domino games are played by two or more players, some can be played solo. Dominoes are usually arranged in a line on the playing surface, and basic instructions for doing so are listed on this site under Line of Play.

Whether the dominoes are in the form of straight or curved lines, grids that form pictures when they fall, stacked walls, or 3D structures such as pyramids, the creation of such structures is one of the most enjoyable aspects of the game for most players. The creation of this art requires a keen eye and considerable patience, however, as the dominoes must be carefully balanced to prevent them from falling over.

The use of dominoes in a figurative sense grew out of the politics of the Cold War in the 1950s and 1960s. During a press conference, President Dwight Eisenhower explained America’s decision to offer financial support to the Ngo Dinh Diem government in South Vietnam by describing it as “a falling domino.” The term domino effect quickly spread beyond political usage and today means any situation where one event can cause others that might seem unrelated to continue in a cascade. The idiom is especially common among writers who are seeking a way to describe the progression of a plot in a novel. The ability of a single action to trigger an entire chain of events, often in unexpected and unpredictable ways, is a key element in creating the excitement and suspense of a compelling plot.