1d9

1d9 refers to the dice notation for rolling a single nine-sided die. The die is expected to produce an integer from 1 to 9, with each value having equal probability if the die is fair. In practice, a true fair 9-sided die is not one of the standard Platonic or Archimedean shapes, so physical 1d9s are typically irregular polyhedra designed to balance faces or are implemented as specialized dice by manufacturers. Because there is no universally agreed-upon standard shape for a 9-faced die, designs can vary between makers.

Usage and purpose: A 1d9 roll is used in tabletop role-playing games, probability experiments, and some board games where a uniform 1–9 outcome is needed. While not as common as dice like d6, d8, d10, or d20, 1d9 appears in certain game systems and probability exercises that require a non-standard range of results.

Combination with other dice: Some game manuals and dice sets omit a true 1d9 and instead pair other dice to achieve similar outcomes, or they rely on dice-polynomial tables. When a dedicated 1d9 is not available, players often simulate it by rolling a d10 and rerolling any result that would yield an invalid outcome (for example, rerolling 0) to obtain a uniform distribution over 1–9.

Reading and notation: In printed materials or digital tools, “1d9” is read as one roll of a nine-faced die, producing a result between 1 and 9. Like other nonstandard dice, its practical use depends on whether a fair physical form is available or whether a suitable simulation method is used.

See also: dice notation, polyhedral dice, random number generation.