Dominoes are square tiles that can be played edge-to-edge against each other to form a long chain. Each domino has a pattern of spots, or pips, on one side and blank or identically patterned on the other. These pips are used to identify the domino and determine its position in the line of play. Some domino games include a score, which is determined by counting the number of pips at the ends of the line of play.
The domino effect is a term that refers to the tendency of one domino to cause others to fall. This phenomenon is particularly useful when applied to human behavior. For example, when a person sets out to make her bed four days in a row, it’s easy to see how that single act can set off a sequence of other tasks that must be done, including laundry, reorganizing Tupperware and cleaning the bathroom.
Like playing cards, of which they are a variant, dominoes have identifying marks on one side and are blank or identically patterned on the other. Depending on the game, dominoes may be divided into two or more squares. Some squares may be marked with an arrangement of spots, or pips, similar to those on a die. The pips on a domino are typically separated by a line or ridge to prevent them from being mixed up with each other.
Each player draws the number of tiles for his hand allowed by the rules of the particular game, adding them to the dominoes in his hand. This group of dominoes is called the stock, and it is reshuffled after every player makes his play. When a player draws more than the number of tiles he is permitted to take, it is called an overdraw. The extra dominoes are taken by the player to his right without looking at them and returned to the stock.
When a player places a tile, it must be positioned so that the open end of the domino matches an end of a previous tile placed on the table. The arrangement of the matching ends is known as the line of play or layout, and basic instructions are listed here under Line of Play for each game.
In many domino games, the first tile played is known as the lead. The word lead is also sometimes used to refer to the opening move made by a player, which is called the set or down. The word lead can also be used to refer to the first domino played in a turn, or to any tile played on top of a double.
Standing a domino upright gives it potential energy, which is stored in its shape and position. As the domino falls, much of this energy converts to kinetic energy, which gives it the push needed to knock over the next domino. Energy continues to transfer from domino to domino until the last one falls. A physicist at the University of Toronto, Stephen Morris, describes this process as a “domino chain reaction.” The energy stored in each domino is transferred to the next one and then to the next until the whole domino chain collapses.