The format used by roleplayers to determine the number of dice, type of dice, and modifiers used for a particular skill check, attack roll, or other random occurance in a roleplaying game.

x = number of dice to be rolled

d = stands for "Dice". Pronounced "dee".

y = type of dice to be rolled. Typically 4, 6, 8, 10, 12, 20, or percentile (100), although other types may be used by rolling one of the standard types and dividing the outcome by a predetermined number (to get d2, you would roll a d4, then divide by 2, rounding up).

z = a constant modifier to the die roll. After all dice are rolled and totaled, this modifier is added (or in some cases, subtracted) to get a final total.

Example: 3d6+1
Three six-sided dice would be rolled, and then a modifier of one would be added. If the initial roll came up 4, 2, and 5, the final total would be 12 (4+2+5+1).

Although it is most common to add up all dice for a final total, some game systems use other procedures, for example taking only the highest roll of all dice, then adding any modifiers.