Historical Rules · 15 February 2021
Rule 107.4h
Official source text from the 15 February 2021 Rules release
When used in a cost, the snow mana symbol {S} represents a cost that can be paid with one mana of any type produced by a snow source (see rule 106.3). Effects that reduce the amount of generic mana you pay don’t affect {S} costs. The {S} symbol can also be used to refer to mana of any type produced by a snow source spent to pay a cost. Snow is neither a color nor a type of mana.