The domino effect, in which a single event can trigger a chain reaction that affects everything that comes afterwards, is a popular metaphor for explaining how things can snowball in unexpected ways. In the real world, the effects of a domino are often more complicated and nuanced than this simple image suggests. Nevertheless, the concept of domino has become an important part of human culture and is used to illustrate many concepts in social science, business, and politics.
In mathematics, a domino (also called a polyomino) is a plane polyhedron with two equal sides connected edge-to-edge. It is also the name of a family of games and other recreational activities that use such polyhedra.
Domino is a type of tile game with very simple rules: each player places a domino on the table so that one side of the domino shows a number (usually a single digit) and the other side shows a different number. The player then plays another domino so that its end touches the end of the first tile, adding to the line of play, which is normally a line of multiple tiles that continue to increase in length.
Players take turns playing a domino, either in the order specified by the rules of the particular game or by whoever holds the highest-ranking double. If no player holds a higher-ranking double, the player holding the heaviest single begins the next game.
Most domino games fall into one of four categories: bidding games, blocking games, scoring games, and round games. The goal of most of these games is to empty a player’s hand by playing tiles and blocking opponents’ play. In blocking games, such as bergen and muggins, players compete to place a domino so that it touches one end of the chain or other dominoes already in play. Scoring games, such as lincoln and mexican train, are similar to scoring card games in that the winner determines points by counting the number of dominoes in the losing players’ hands.
Historically, domino sets have been made from a variety of materials including bone, silver lip ocean pearl oyster shell (mother of pearl), ivory, and dark hardwoods such as ebony. Modern sets are often made from polymer, though wood and metal are still popular choices. Decorative, more artistic domino sets are also available, and these can be particularly beautiful in the case of natural materials like ebony, which is highly polished to create a smooth, matte finish.
While it may be possible to produce a set of dominoes with as few as twenty-four different pips on each end, this is extremely rare; most sets have fifty-two or more pips on each end. To increase the number of unique combinations, domino sets are “extended” by adding additional ends with increasing numbers of pips. Some of the most common extended sets include double-nine, double-12, and double-18. Much larger sets are theoretically possible, but these would require far more tiles than is usually required for any given game.