A domino is a small tile that represents the roll of two dice. The tile, commonly called a bone, is rectangular with a line down the center. Each end of the tile contains a number. In the most popular domino set, the double-six, the numbers vary from 0 (or blank) to 6. This produces 28 unique tiles, as shown in the diagram on the right.
A common domino size is 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 thick enough to be able to be stood on edge.
Dominoes are referred to by the number of dots (or pips) on each end, with the lower number usually listed first. Thus, a tile with a 2 on one end and a 5 on the other is referred to as a "2-5". A tile with the same number on both ends is called a "double" (or doublet), so a "6-6" is referred to as "double-six". A double-six is the "heaviest" domino; a double-blank is the "lightest" domino value.
Tiles which have ends with the same number of dots are members of the same "suit". In a double-six set, there are seven suits (blank, 1, 2, 3, 4, 5, 6), each with seven members (0-5, 1-5, 2-5, 3-5, 4-5, 5-5, & 5-6) make up the "fives" suit, for instance. Except for the doubles, each tile belongs to two suits.
In addition to the standard double-six domino set, larger-sized sets are also available. Popular sizes include the double-nine (55 tiles), double-twelve (91 tiles), double-fifteen (136 tiles), and double-eighteen (190 tiles). The larger sets are used in some of the more complicated games. They can also be used to add variety to the simpler games, or to allow more people to play them.
For further information on the development and evolution of dominoes, check out our History of Dominoes. For help with domino terminology, our Dominoes Glossary has information on common domino terms and expressions.
