A domino is a flat, thumb-sized rectangular block that is marked with an arrangement of dots or pips on one side and blank on the other. 28 such pieces comprise a complete set of dominoes. Dominoes are used to play a variety of games, most of which involve matching the ends of two adjacent or touching dominoes in a line of play. Once the first domino is toppled, it sets off a chain reaction that continues down the line of play until all of the dominoes are set up. Dominoes may be laid in straight lines or angular patterns, depending on the game. Dominoes can also be stacked to form 3D structures like towers and pyramids.
A player begins a domino game by drawing a domino from the stock, which is a stack of unplayed tiles. The player who draws the heaviest tile makes the first play, according to the rules of the particular domino game. If a tie exists, it is broken by drawing new tiles from the stock until a domino with a higher value is found. The next player places his or her domino on an open end of the line of play, which is usually referred to as the layout or string. The remaining dominoes remain in the stock until the layout or string is completed.
When the last domino is placed, the number of sides on the adjacent dominoes determines whether a new piece may be added to the domino chain. If a new piece can be played on the end of the domino chain, then it must be done so that the two matching sides are completely touching. This ensures that the domino does not fall off the table and it also prevents the domino from being flipped over to its back, which would disrupt the chain. In most domino games, a new tile is added to the chain after each double played if it is not a spinner. A spinner is a double that can be played on all four sides and, therefore, counts as two ends of the domino chain.
There are many different types of domino games, and the basic instructions given here for a single-player game apply to most. However, several games require players to draw a hand of dominoes from the stock, and the rules of those games differ greatly.
In the 1977 Frost/Nixon interviews, Richard Nixon defended the United States’ destabilization of the Allende regime in Chile and Cuba by reference to the Domino Theory, which held that Communist Chile and Communism in Cuba would lead to a red sandwich in which Latin America was trapped between the communists and the United States. This theory was also cited in the 1980s as the rationale for military intervention in Central America and the Caribbean.
A variety of ways can be arranged to create a layout or string of dominoes, and the resulting pattern is sometimes used to form art. Decorative patterns of dominoes can be painted on walls, in a frame, or sculpted into three-dimensional structures. A more ambitious project is to create a domino layout or track with the intent of making a specific image when the dominoes are placed on it.