Armor Class

Armor class (AC) is a number representing a creature's ability to avoid being hit in combat. An opponent's attack roll must equal or exceed the target creature's Armor Class to hit it.

Armor Class = 10 + all modifiers that apply

Modifiers typically include:
 * armor bonus
 * shield bonus
 * natural armor bonus
 * deflection bonus
 * dodge bonus
 * Dexterity modifier
 * size modifier