domino

Domino is a rectangular tile used in dominoes, a family of games. Each tile, or domino, is a rectangular playing piece divided into two square ends by a central bar. Each end bears between zero and six pips (dots) in the standard double-six set, though larger sets use up to double-nine, double-twelve, etc. A double tile has the same number of pips on both ends.

A domino set comprises a complete collection of tiles; the double-six set has 28 tiles. Gameplay typically involves matching the pips on adjacent ends to form a continuous chain; players draw tiles and try to play all tiles or score points based on the remaining pips in opponents' hands. Rules vary by regional variants, including blocking, drawing, and scoring methods.

Originating in China, dominoes reached Europe in the 18th century and became popular in Italy and Britain; modern sets are standardized and widely used in many countries with numerous local variants.

In physics, the term domino is used in the domino effect to describe a chain reaction where falling tiles knock over others. The term is also used metaphorically to describe cascading failures in systems.