A die (plural "dice") is really any solid object with markings on each face that can be used to create a random number. Very useful when playing games of chance!
In mathematics we say "fair dice" when we mean that there is an equally likely chance of landing on any face.
Most people think of these little cubes
when we say "dice" ...
... but all of the Platonic Solids can make fair dice!
Because the faces are all the same, there is an equal chance of landing on any face.
So, using the platonic solids we can have dice with 4, 6, 8, 12 or 20 faces!
But with some imagination we can actually make fair dice with any number of faces we want.
How about these interesting dice?
Or this 10-sided one.
Or this 20-sided Roman die that is 1,800 years old.
So long as there is an equally likely chance of landing on any face then they are Fair Dice.