Thac0

Thac0, short for "To Hit Armor Class 0," is a gaming term used in classic Dungeons & Dragons to determine how easy or hard it is for a character to hit an opponent. It represents the lowest roll needed on a 20-sided die (d20) to successfully land an attack against an opponent with an Armor Class (AC). As your character becomes more skilled or equipped, your Thac0 number decreases, making it easier to hit enemies. A lower Thac0 indicates better accuracy—it’s a way to measure your attack proficiency in relation to your target’s defenses.