Domino is a word used to refer to a series of flat, thumb-sized blocks bearing an identity-bearing face that may be blank, patterned or marked with one to six spots or dots (the plural of domino is dominoes). The identifying mark on a domino is called an alveolar or pip; it is usually a small dot. The other face of the domino, called an apex, is generally a small round crest of an arc or crescent shape that resembles the head of a die. A domino is normally twice as long as it is wide.
Dominoes can be played with a variety of rules and scoring systems, ranging from simple matching games to positional and scoring games. Some games use the entire domino set and are played in partnership, whereas others limit play to certain numbers of tiles. For example, in a game of Concentration, the players are each given 12 tiles at the start of the game, and they must place their tiles on the table so that they match each other in a chain that continues to grow longer and larger. In this way, a partner can win by placing the last domino that has a number showing on both its ends. This example demonstrates the commutative property of addition and reinforces the idea that the addends can be written in any order, which helps students bridge the gap between using moveable manipulatives like cubes and relying solely on symbolic representations such as numbers and equations.
The name “domino” is derived from the Latin dominovum, meaning “to rule.” A more obscure sense of the word referred to a hooded cloak with a mask worn together at masquerades. The word and the game are both thought to have appeared in France shortly after 1750.
A wide range of dominoes have been made from natural materials such as bone, silver lip ocean pearl oyster shell (mother-of-pearl or MOP), ivory, and a dark hardwood like ebony, with contrasting black or white pips inlaid or painted on each piece. In recent years, domino sets have been crafted from non-natural materials such as ceramic clay, stone (e.g., marble or soapstone); metals; and frosted glass or crystal. These sets often have a more distinctive appearance and feel than those of traditional MOP, ivory or wood dominoes, and can cost significantly more.
Despite the complexity of some domino games, most of them are relatively simple to learn. A number of books describing the rules of domino games are available. The most extensive is The Great Book of Domino Games by Jennifer A. Kelley, which describes many of the most popular and well-known games, along with some more unusual ones. In addition, several websites provide rules for many domino games and can offer advice on how to make or purchase a particular type of domino set. Moreover, there are numerous apps that allow users to create and play domino games on their computers or smart phones.