Dice (singular: die) are numbered polyhedra used to obtain a random whole number. Dice were originally made of bone, crystal, ivory, rock and wood. Today they're sometimes also made of glass and plastic. The most commonly used dice are regular polyhedra, which have either four, six, eight, twelve or twenty sides.
Six sided dice often have have a number of dots on their faces; while dice with more sides usually have numbered faces. A four sided die, a tetrahedron, has a point facing upwards when it lands on a surface; so its value is read off of numbers written around the bottom of the three faces which aren't on the surface. Dice for triple choices are made by numbering a six sided dice with a pair of ones, twos and threes. A die for ten choices is sometimes made by pair numbering a twenty sided die.
A thirty sided die with diamond faces can be constructed from a twelve or twenty sided die by placing the diagonal on the diamond face on each edge of the original die. The other two vertices of the diamond face meet on the line from the center of the die through the center of the face of the original die. Thirty sided dice are often used to randomly obtain a day of the month for a game.
A ten sided die can be made with a pair of five faces originating from both poles of the die. Two ten sided dice are often used together to obtain a random percentile. Another way to obtain a random percentile is with a hundred side die, the Zocchihedron.
Six sided dice are used in a many games of chance like Backgammon and Craps. Most dominos are based on the six sided dice. Role-playing games use a wide variety of dice and usually a large quantity when modeling a battle.
Dice are usually carefully made to obtain a balanced distribution. Much willpower and hope often goes into dice rolling to get a desired outcome. When luck isn't enough; loaded dice are made to obtain a lopsided distribution, to cheat or just for amusement.