A d10 — also called a ten-sided die or, less commonly, a decahedron (technically a pentagonal deltohedron) — is one of several standard polyhedral dice used in gaming. Each type is generally identified by the use of the letter "d" (for "die" or "dice") and the number of sides the die features, with 0 representing 10. Multiple dice are connoted by an additional number prefixing the D. So rolling five 10-sided dice would be noted by writing 5d10.
The d10 is the only die type used in the Storyteller System and the Storytelling System, the proprietary in-house system of White Wolf. It's also remarkable for being the only die type which is not a classical polyhedron. Two d10s of different colours are also often used in place of a d100 in the d20/OGL system.
Dice Used in Roleplaying Games