A domino is a flat thumb-sized, rectangular block marked on one face with from two to six groups of dots or pips: 28 such pieces make up a complete set. A domino set is used to play various games, the most familiar being a simple game of matching ends of adjacent pieces in lines and angular patterns, or to form large structures such as towers. Other types of games involve placing tiles in a layout and then scoring points by laying them down in lines or a pattern, either in the form of a single line or an asymmetrical arc.
When the domino principle is applied to social and personal issues, it refers to a situation where an initial setback triggers a chain reaction that affects more than just the individual involved. For example, if someone begins making their bed every day, it may lead to a series of other small actions that reinforce the idea that they are a “bedmaker.”
In computer programming, a domino is a software tool for expressing atomic increments in a program. It can also be used to model a network and its dependencies. The domino principle is often compared to the network effect, which is a positive economic phenomenon that occurs when an initial investment leads to increased value for a product or service due to its effects on other customers and on the supply of that product or service.
For example, a network that is connected to the Internet can be said to have a domino effect. If one computer in a network is compromised, all other computers on the same network will be susceptible to attack as well. In this way, the network itself becomes a victim of its own success.
In the past, domino sets were made from bone, silver lip ocean pearl oyster shell (mother of pearl), ivory or a dark hardwood such as ebony, with contrasting black or white pips inlaid or painted on the edges. More recently, dominoes have been manufactured in a variety of other materials, including stone (such as marble or granite); other woods such as ash, spruce, oak or redwood; metals; and even ceramic clay.
Most domino sets have open ends, which allow additional tiles to be placed on top of them. Some games are played with a limited number of open ends, requiring the player to connect all of the exposed sides of a double before scoring points. Other games require connecting only the abutting long sides of a double.
There are a wide variety of domino rules and a domino dictionary is available to help players learn the rules of various games. Some of the most popular include: