A domino is a small rectangular block with two groups of spots (or dots) on one side. It is used for playing many games that involve stacking other dominoes on top of each other in long lines. When a domino is knocked over, it causes the rest of the line to tip over, and so on. These chains of dominoes can create complex shapes and patterns, and they are a great example of the “domino effect,” where a small action leads to much bigger effects.

Traditionally, dominoes are made of bone, silver lip ocean pearl oyster shell (mother of pearl), ivory, or a dark hardwood such as ebony. They may be painted, inlaid with a metal or other material, or they can have the pips carved or scratched directly into the surface. Modern sets are usually made of plastic or a similar polymer, although some are still made of natural materials.

The most basic Western domino game is a block-and-draw game for two or more players. The pieces are shuffled and stacked on-edge before the players; then each player draws at random from the total number of dominoes needed for the game, typically seven. The player with the highest total pips counts draws first and places the first tile on the table, generally a double-six (this is determined either by drawing lots or by choosing the heaviest tile in the hand). The remaining tiles are left behind, called the boneyard; they can be drawn from later in the game.

Dominoes are normally twice as wide as they are tall. This makes them easy to re-stack when not in use. Each domino has a line in the center that divides it visually into two squares, called ends; each end has a different value, from six pips to none or blank. The two values are combined to form a suit, such as the suit of threes or the suit of tens. A single domino may belong to both suits.

In most domino games, a tile is considered to have an open end when it has an even number of pips on both sides; a double is considered an open end when it has a pair of matching numbers on both ends. The open ends of the tile are used for connecting other dominoes in the game, which allows a chain to grow. Domino chains may be placed in any direction depending on the rules of the game, the constraints of the playing surface, or a player’s whims.

In the most popular domino games, a player takes turns placing dominoes on the layout, starting with a tile of a certain value. Other tiles are then played to the ends of the chain, and the game continues until a player has no more pieces in his or her hand. Then the player declares a winner. There are many variations on the theme of this simple game, with different rules and strategies for winning.