Modifier
Also known as: bonus, penalty, mod
Definition
A number added to (or subtracted from) a dice roll. Modifiers come from attributes, skills, equipment, magic, or situational bonuses/penalties.
How it works in different systems
D&D 5e: Modifiers from abilities, proficiency, magic items. Advantage/disadvantage replaces most situational mods.
Call of Cthulhu 7e: Bonus/penalty dice: roll extra d10 for tens digit, take best/worst.
Vampire V5: Fewer modifiers - situations usually add/remove dice from pool instead.
GURPS: Heavy modifier system with tables for many situations.
Example
“Attacking with a longsword: roll 1d20 + Strength modifier (+3) + proficiency bonus (+2) = 1d20+5. You need to meet or beat the target's AC.”
Common Mistakes
- Stacking bonuses that don't stack (in 5e, same-named bonuses don't stack)
- Forgetting situational modifiers like cover or advantage
- Adding modifiers to damage when they shouldn't apply