A domino is a small rectangular block of wood or plastic, used as a gaming object. Its face is blank or marked with an arrangement of dots resembling those on dice, and it is distinguished from its companion by a line that separates the two sides into squares, each identified by a number of spots, called “pips.” The value of a domino may be inferred from the total sum of its pips, and its rank is indicated by its size. Dominoes are also known as bones, cards, men, or pieces. Traditionally, the 28-piece set of dominoes represented all the possible outcomes of throwing two six-sided dice.
The basic game of domino requires the players to lay tiles in a line, building up chains of combinations of numbered ends that eventually lead to a finished line. The tiles are usually placed on-edge in front of the players, so that each player can see all of his own tiles but cannot easily see the values of other tiles. When a tile is laid, it can only be matched with another with the same patterned side; if no matching tiles are available, then the next player takes his turn.
Each player draws his tiles from the box, and one begins play by placing the first tile on the table. The first player may be chosen by drawing lots or by selecting who holds the heaviest hand. Each of the other players then places his remaining tiles, one at a time, in front of him. Then the players draw additional tiles until they have seven in their hand, which is the minimum number of tiles required for a full game.
When a domino is placed, the matching end of that tile must be touching a full end of another domino that is already in the layout. This allows a domino chain to develop in a snake-like fashion, depending upon the whims of the players and the limitations of the playing surface. In addition, a domino must be positioned in such a way that the two matching ends are adjacent.
A domino has potential energy based on its position, but as it falls and is picked up by another domino, much of that potential energy is converted to kinetic energy, the energy of motion. The kinetic energy of the falling domino is transmitted to the next domino, providing the push needed for it to fall as well. This continues for as many dominoes as there are in the line, and can result in a spectacular display of energy conversion. This demonstration is often used as an educational tool to illustrate how physics works. In fact, many schools have domino rallies to teach children about energy conversion.