A domino is a small rectangular block with either blank or marked surfaces resembling those on dice. A domino is normally twice as long as it is wide, allowing it to be stacked on top of one another. The number of spots or pips on each side determines its value, which may range from six pips down to none or blank. Dominoes are often arranged in sets for playing games with rules that govern each game’s order of play, scoring, and winning.

While the word domino has only been in use since 1750, the concept is rooted in ancient history. The word originally denoted a long, hooded cloak worn together with a mask at carnival season or at a masquerade. It has also been suggested that the term referred to a priest’s black domino contrasting with his white surplice.

A variety of domino games are played with a set of tiles called a “domino board” or “table”. The most popular, especially for casual players, are those involving the number nine and twenty-two, although many other variants exist. Most games are played by two or more people and may require a number of sets depending on the size of the group.

Before the start of a game, each player draws the number of dominos indicated by the rules of the particular game being played. The player with the highest domino drawing begins the first turn of play. This player may also be referred to as the setter, the downer, or the leader.

Each domino is then placed on the table, forming a line of play. Unless otherwise specified, a domino must be placed so that its matching end is touching another tile, and the other end of the domino must be open for further play (this is known as an open double). A piece may be played to a double on any of the four sides of the layout, but most games only allow additional tiles to be added along the longest side of a double (the shortest side).

In some games, the ends of the line of play are counted in the calculation of a win or loss. This is done by counting the pips on the ends of each of the dominos in the line of play, as well as any additional doubles that have been played (depending on the rules of a game, a double is considered a spinner if it can be played on all four sides).

In addition to the standard domino materials of bone, silver lip ocean pearl oyster shell (mother of pearl), or ivory, a set of dominoes can be made from other natural and man-made materials such as stone (e.g., marble or granite), other woods such as ebony, or metals like brass and pewter. Typically, these sets are more expensive than those made from polymer. In recent years, some designers have even used frosted glass and ceramic clay to create domino sets with a more unique look and feel.