Definitions

# dominoes

[dom-uh-noh]
dominoes, game played with a set of rectangular pieces (usually 28 in number) called dominoes. Each piece (made of wood, bone, ivory, plastic, or other material) has one blank face and one face marked with pips, or dots. The marked faces are divided into halves, each half containing (in a 28-piece set) from 0 to 6 pips in every possible combination—0-0, 1-1, 1-0, and so on. The most common version of dominoes is the draw game wherein two to four players pick a specified number of face-down dominoes. The object of the game is to match the number on one domino half to that of the half already played on the table. The first to dispose of all his or her dominoes wins. The game has been traced as far back as 18th cent. Italy where it enjoyed great popularity among the idle courtiers of Venice.

Game of several variations played with a set of flat rectangular blocks (dominoes) whose faces are divided into two equal parts that are blank or bear from one to six dots arranged as on dice faces. The usual set consists of 28 pieces. Dominoes in China may date to the 12th century AD; the Eskimos have also long played a domino-like game. There is no record of dominoes in Europe before the mid-18th century. The principle in nearly all modern dominoes games is to match one end of a piece to another that is identically or reciprocally numbered. The game may be set at 50 or 100 points.

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Dominoes (or "dominos") generally refers to the individual or collective gaming pieces making up a domino set (sometimes called a deck or pack) or to the subcategory of tile games played with domino pieces. In the area of mathematical tilings and polyominoes, the word domino often refers to any rectangle formed from joining two congruent squares edge to edge. The traditional Sino-European domino set consists of 28 dominoes, colloquially nicknamed bones, cards, tiles, tickets, stones, or spinners. Each domino is a rectangular tile with a line dividing its face into two square ends. Each end is marked with a number of spots (also called pips) or is blank. The backs of the dominoes in a set are indistinguishable, either blank or having some common design. A domino set is a generic gaming device, similar to playing cards or dice, in that a variety of games can be played with a set.

## Construction and composition of domino sets

European-style dominoes are traditionally made of ivory, bone, or a dark hardwood such as ebony, with contrasting black or white pips (these can be in inlay or painted). Alternately, domino sets have been made from many different natural materials: stone, like marble, granite or soapstone; other hardwoods such as ash, oak, redwood and cedar; metals like brass or pewter; ceramic clay, or even frosted glass or crystal. These sets have a more novel look, and the often heavier weight makes them feel more substantial, but such materials and the resulting products are usually much more expensive than polymer materials.

Modern commercial domino sets are usually made of synthetic materials, such as ABS or polystyrene plastics, or Bakelite and other phenolic resins; many sets approximate the look and feel of ivory while others use colored or even translucent plastics to achieve a more contemporary look. Modern sets also commonly use a different color for the dots of each different end value (one-spots might have black pips while two-spots might be green, three red, etc.) to facilitate finding matching ends. Occasionally, one may find a domino set made of card stock like that for playing cards. Such sets are lightweight, compact and inexpensive, but like cards are more susceptible to minor disturbances such as a sudden breeze.

The traditional set of dominoes contains one unique piece for each possible combination of two ends with zero to six spots, and is known as a double-six set because the highest-value piece has six pips on each end (the "double six"). The spots from one to six are generally arranged as they are on six-sided dice, but because there are also blank ends having no spots there are seven possible faces, allowing 28 unique pieces in a double-six set.

However, this is a relatively small number especially when playing with more than four people, so many domino sets are "extended" by introducing ends with greater numbers of spots, which increases the number of unique combinations of ends and thus of pieces. Each progressively larger set increases the maximum number of pips on an end by three, so the common extended sets are double-nine, double-twelve, double-fifteen and double-eighteen. Larger sets such as double-twenty-one can theoretically exist but are rarely seen in retail stores, as identifying the number of pips on each domino becomes difficult, and a double-twenty-one set would have a staggering 253 pieces, far more than is normally necessary for most domino games even with eight players.

## History

Domino pieces were historically carved from ivory or animal bone with small, round pips of inset ebony. The game's name comes from the pieces' resemblance to Venetian Carnival masks known as domini, which were white with black spots. These masks were so named, in turn, because they resembled French priests' winter hoods, being black on the outside and white on the inside. The name ultimately derives from the Latin dominus, meaning "lord" or "master."

The oldest domino sets have been dated from around 1120. Modern dominoes, as most of the Western world knows them, however, appear to be a Chinese invention. They were apparently derived from cubic dice, which had been introduced into China from India some time in the distant past. Each domino originally represented one of the 21 results of throwing two dice. One half of each domino is set with the pips from one die and the other half contains the pips from the second die. Chinese sets also introduce duplicates of some throws and divide the dominoes into two classes: military and civil. Chinese dominoes are also longer than typical European dominoes. Over time Chinese dominoes also evolved into the tile set used to play Mah Jong, a game which swept across the United States in the early to mid 1920s and has enjoyed moderate popularity, especially in its "solitaire" form, since that time.

The early 18th century witnessed dominoes making their way to Europe, making their first appearance in Italy. The game changed somewhat in the translation from Chinese to the European culture. European domino sets contain neither class distinctions nor the duplicates that went with them. Instead, European sets contain seven additional dominoes with six of these representing the values that result from throwing a single die with the other half of the tile left blank.

## Tiles and rules

### Tiles and suits

Bones are generally named for the number of dots on the two ends of the bone. A bone with a 2 on one end and a 5 on the other end is called the two - five, for example. Bones that have different numbers on the two ends are called singles or "blank" - number, and bones that have the same number on both ends are called doublets, doubles, or "double" - number.

Bones that share a common number of spots on one end are said to be of the same suit. In a double-six set, for example, 1–0, 1–1, 1–2, 1–3, 1–4, 1–5, and 1–6 all belong to the suit of one. All dominos, except for the doubles, belong to two suits. The 1–2, for example, belongs to the suit of one and the suit of two. All doubles belong to one suit only by this definition. An alternate definition of suit allows all dominoes to have two suits, by counting the set of all doublets as an additional suit.

### Ranks

The value of each end of a bone is determined by the number of spots on the end, with zero (blank) being the lowest and six being the highest. The rank of a bone is determined by the combined number of pips on the two ends. This rank is sometimes referred to as the bone's weight so that a higher ranking bone is called a heavier bone while a lower ranking bone is called lighter.

### Domino Sets

There are currently five major domino sets commercially available. They are Double Six, Double Nine, Double Twelve, Double Fifteen, and Double Eighteen, which is the largest commonly-available set. Here are the number of tiles and points (pips or spots) in each set.

• Double 6: 28 tiles, 168 pips
• Double 9: 55 tiles, 495 pips
• Double 12: 91 tiles, 1092 pips
• Double 15: 136 tiles, 2040 pips
• Double 18: 190 tiles, 3420 pips

These numbers may be computed quite easily using triangular numbers: for Double n dominoes, there are T(n) = (n+1)(n+2)/2 tiles and n T(n) = n(n+1)(n+2)/2 pips. Generally the most commonly used sets are Double Sixes and Double Nines, though the other three sets are more popular for games involving several players or for players looking for long domino games.

## Game variations

### Common games

Most domino games are block games or draw games. Generally, the object is to play all of your dominos before the other players, and/or collect as many points as possible from the other players or teams. In team play the first player to play all his dominos wins for his or her team. The winning player, or team, collects the combined points or pips of the other players or team.

In the most common versions of the game, the tiles are shuffled face down, and each player picks seven (7) tiles. The player with the highest double leads with that double, for example "double six". If no one has it the next highest double is called - "double five?", then "double four?", etc. until the highest double in any of the players hands is played. If no player has an "opening" double, the next heaviest domino in the highest suit is called - "six - five?", "six - four?". In some versions of the game the players take turns picking dominoes from the boneyard until an opening double is picked and played; in other versions the hand is reshuffled and each player picks seven dominos.

Playing the first bone of a hand is sometimes called setting, leading, downing, or posing the first bone. Dominoes afficinadoes often call this procedure smacking the bone down. After each hand the bones are shuffled, and each player in draws the number of bones required (7). After the first hand, the winner or winning team of the previous hand is allowed to pick their dominos first, and begins by playing any domino in his or her hand.

Play generally proceeds "clockwise", but by prior consensus can proceed "counter-clockwise". The next player, and all players in turn, must play a bone with an end that matches one of the open ends of the layouts. In some versions of the games the pips or points on the end and the section to be played next to it must add up to a given number; [For example in a double six set the "sum" would be six (6), requiring a "blank" to be played next to a "6," a "1" next to a "5", a "2" next to a "4", etc.]

The stock of bones left behind, if any, is called the boneyard, and the bones therein are said to be sleeping. In draw games, players take part in the bone selection, typically drawing from the boneyard when they don't have a "match" in their hand.

Generally, if a player inadvertantly picks up and sees one or more extra dominos, those dominos becomes part of his or her hand.

In block games, players who cannot match or play, on their turn must forfeit the turn by knocking or (passing), accomplished by tapping twice on the table or by saying, "go" or "pass". In draw games, players who cannot match or play, must draw bones from the boneyard until obtaining a playable bone. If the boneyard is exhausted, the player knocks.

Play continues until one of the players has played all the dominos in his or her hand, (and calls "out!", "I win", or "domino!") and wins the hand, or until all the players are blocked and no legal plays are left. This is in some areas referred to as a lockdown or "sewed up". In a common version of the game, the next player after the block, picks up all the dominoes in the boneyard, as if trying to find the (non-existant) match. If all the players are blocked, or locked out the player with the lowest hand / pip count wins. In team play, the team with the lowest individual hand wins. In the case of a tie, the first of tied players or the first team in the play rotation wins.

In games where points are accrued, the winning player scores a point for each pip on each bone still held by each opponent, or the opposing team. If no player went out, however, the win is determined by the lightest hand; sometimes only the excess points held by opponents. A game is generally played to 100 points, the tally being kept with paper and pencil. In more common games, mainly urban rules, games are played to 150, 200, or 250 points. In some games the tally is kept by creating houses, where the beginning of the house (the first ten points) is a large +, the next ten points are O, and scoring with a 5 is a /, and are placed in the four 'corners' of the house. In some versions, if a lockdown occurs then the first person to call the lockdown will gain the other players bones and add the amount of the pips to their house.

### Games using more dominoes

With bigger domino sets, especially with the Double Fifteens and Double Eighteens, it is possible to have more players. Double 9s is good for 4 to 6 players and each player would start with 7 dominoes in their hand. Double 12s, 15s, and 18s are good for up to 10 to 15 players, each with 7 dominoes. If you have fewer players and more dominoes, start with more dominoes in each player's hand, but leave enough dominoes in the bone pile to draw from. When using the larger sets, make sure you have plenty of playing room as they can spread out considerably.

Double 6s = 7 rounds, double 9s = 10 rounds, double 12s = 13 rounds, double 15s = 16 rounds, double 18s = 19 rounds.

### Other games

There are also a variety of other games played with dominoes. Some are simple memory games like Concentration (based on the card game of same name), some are complex, and some are simple solitaire games. Common games include Private Trains and Chicken Foot.

A popular domino game in Texas is 42. The game is similar to the card game spades. It is played with four players paired into teams. Each player draws seven dominoes, and the dominoes are played into tricks. Each trick counts as 1 point, and any domino with a multiple of 5 dots counts toward the total of the hand. 35 points of "five count" + 7 tricks = 42 points, hence the name.

Also, in the Caribbean, there are other common games which involve four players in which the players can play as partners or as individuals. In partners, the partners sit across from each other and all hands can not be seen by the other players. The game is started by shuffling the dominoes or 'cards' and each player pulling seven cards. The double six is then played and play continues to the starter's right side. If a player can not play then he is passed and it is the next player's turn. The object is for a team to win by one of the players running out of dominoes. The winning team is awarded a point and then restart the process by shuffling and pulling a new hand and then starting with any domino either partner wishes to play. The game goes on till one team reaches six points. Double points are awarded when you get 'key'. This happens when your last card is the only card that can be played on both ends. Also when a player pulls five doubles all players put their dominoes back and pull new hands, the following game is played for 2 points and the double six is started by the player who has it. This variation is called Partners, where the other variation is called Cut-Throat, where each player plays for himself, in which all the same rules apply as in partners. This form of dominoes is most common in Jamaica and the Cayman Islands.

## Competitive play

Dominoes is played at a professional level, similar to poker, and matches and tournaments are often televised in Latin America. Numerous organisations and clubs of amateur domino players exist around the world. Some organisations, including the International Federation of Dominos and the Fédération Internationale de Domino (FIDO), organise international competitions. The 2007 FIDO domino world champion is the Swiss college student Alex Joss.

## Other uses of dominoes

Other than playing games of strategy, another common pastime using domino tiles is to stand them on edge in long lines, then topple the first tile, which falls on and topples the second, which topples the third, etc., resulting in all of the tiles falling. Arrangements of millions of tiles have been made that have taken many minutes to fall. By analogy, similar phenomena of chains of small events each causing similar events leading to eventual catastrophe are called domino effects. The phenomenon also has some theoretical relevance (amplifier, digital signal, information processing), and this amounts to the theoretical possibility of building domino computers.

The Netherlands has hosted an annual domino toppling exhibition called Domino Day since 1986. The event held on November 18, 2005 knocked over 4 million dominoes. Another new record was set at 4,079,381 stones on November 17, 2006.

At one time, Pressman Toys manufactured a product called Domino Rally that contained tiles and mechanical devices for setting up toppling exhibits.

Dominoes are not just for games these days. Domino Art is the art of decorating domino tiles. First the domino is sprayed with an acrylic paint. Once it has dried, it is stamped with a rubber stamp and then various colors of ink are applied. Some artists drill holes in them before spraying and wire wrap the finished piece.

Dominoes are also commonly used as components in Rube Goldberg machines.

## Dominoes in Unicode

The Unicode range for Dominoes is U+1F030 .. U+1F09F. Grey areas indicate non-assigned code points.