A domino is a small rectangular wood or plastic block with one face bearing an arrangement of dots resembling those on dice. The other face is blank or marked by a single dot. Twenty-eight such blocks form a complete set of dominoes. The word is also used for any of the games played with them, especially those in which players build chains of dominoes by matching their ends and laying them down in lines or angular patterns.

Dominoes are often used to illustrate the principles of physics, particularly gravity and momentum. Watching a domino effect demonstration is entertaining, but it’s even more interesting to see an accomplished domino artist create an intricate setup and then let it all fall according to the laws of physics. In addition to straight lines and curved lines, these displays can include grids that form pictures when they fall, stacked walls, and 3D structures like pyramids. Some domino artists compete in a kind of domino show, where they set up hundreds of thousands of dominoes and then create a nail-biting sequence that culminates in the final toppling.

The simplest game is to play a domino on a smooth, level surface such as a table or floor. Each player has a hand of dominoes, and the first to play a domino wins the round. Each subsequent player plays a domino to an open end, or “node” of the chain. The total number of pips on the open end determines whether the player scores points, with doubles counting twice. The first player to score a set number of points in a round—usually 61—wins the game.

More skillful gamers enjoy a game called chinese checkers, which is very similar to domino. Each player has a hand of dominoes, but in this game the total number of pips on each open end (with doubles counting twice) is divided by two. The total is then multiplied by the number of spots on a domino, and each player plays a domino to an open node in the chain, or row of dominoes.

A skilled dominoes player is able to make a long, neat and even row of dominoes, which makes for a very pleasing spectacle. The game is also popular in classrooms and schools, where the students practice math skills by counting each domino’s pips as it falls.

The word domino is also used to describe a country that is expected to react politically in a certain way after some event has occurred. For example, after the United States invaded Indochina in 1950, some scholars predicted that China would react militarily by sending troops to reclaim its territory. Others, however, have criticized this theory as flawed because it doesn’t take into account other countries in the region that may have their own views about how a domino should fall. Still, the concept of a domino effect is a valuable tool to use in understanding how political events can change quickly and unpredictably.