Actions, Bonus Actions, and Reactions Rules
The action economy in Dungeons & Dragons 5th Edition is the invisible framework that governs every single round of combat. Three distinct resource types — actions, bonus actions, and reactions — each have specific rules about when they can be spent, what they can do, and how they interact with one another. Getting these straight is the difference between a fighter who attacks twice and one who somehow manages to attack, dash, and shove in a single turn.
Definition and scope
Each creature in D&D 5e gets one action, one bonus action, and one reaction per round of combat. That sounds simple until a player realizes their character has a class feature, a spell, and a magic item all competing for the same bonus action slot on the same turn.
Action is the primary resource. On a turn, a creature can use its action to attack, cast a spell, dash, disengage, dodge, help, hide, ready, search, or use an object — among other options detailed in the D&D 5e Basic Rules. An action is not conditional; every creature has one automatically each turn.
Bonus action is a conditional resource. According to the Player's Handbook (Chapter 9), a bonus action can only be taken if a class feature, spell, or ability explicitly says it uses a bonus action. This is a rule that trips up new players with some regularity: if nothing on a character sheet grants a bonus action, that character simply does not have one to spend. Holding onto an unused bonus action does nothing — it does not carry over.
Reaction is a resource that resets at the start of each turn but can trigger outside a creature's own turn. Opportunity attacks, the shield spell, and the Ready action's resolution all use reactions. A creature starts each round with 1 reaction available, and spending it means no more reaction-based abilities until the start of that creature's next turn.
How it works
The sequence matters. On a creature's turn, it can generally move up to its speed, take one action, and take one bonus action (if available). Order is flexible — a rogue can move, use Cunning Action as a bonus action to hide, then take an action, or flip that sequence entirely.
Three structural rules anchor the entire system:
- Stacking prohibition: A creature cannot take more than one action per turn unless a special rule (Action Surge, for example) explicitly grants an additional action.
- Bonus action independence: A bonus action cannot be used to take an action that normally requires a full action, regardless of timing or intent.
- Reaction triggers: A reaction can only be taken when its specific trigger condition is met — a creature cannot hold a reaction for any arbitrary trigger it invents.
The key dimensions and scopes of D&D page covers how these rules scale across different play contexts, but in standard 5e RAW (Rules As Written), the three resource types are strictly isolated from one another.
Common scenarios
A few situations reliably cause confusion at tables everywhere.
Two-Weapon Fighting: Drawing a light weapon and attacking with it uses the action. The bonus attack from the off-hand weapon uses the bonus action. This means a two-weapon fighter who also has a bonus action feature (say, a rogue's Cunning Action) must choose — the bonus action slot fits only one occupant per turn.
Cunning Action vs. Two-Weapon Fighting: A rogue with two short swords can attack with both weapons or use Cunning Action (Hide, Dash, or Disengage) on their bonus action — not both. This is a deliberate tension in the class design.
Readied Spells: When a caster uses the Ready action to hold a spell, they expend their action and their spell slot immediately. The reaction — used to release the spell when the trigger fires — is then consumed when conditions are met. The spell slot is spent whether or not the trigger occurs, per the Player's Handbook Chapter 10.
Opportunity Attacks: These are reactions triggered by a hostile creature leaving a creature's reach without using the Disengage action. Because opportunity attacks consume the reaction, a fighter who has already cast shield in a round cannot also make an opportunity attack before that turn resets.
Decision boundaries
The clearest way to distinguish the three is by trigger and timing:
| Resource | Trigger | Timing |
|---|---|---|
| Action | Creature's own turn, always available | During the creature's turn |
| Bonus Action | Class/spell/ability must specify it explicitly | During the creature's turn only |
| Reaction | Specific triggering event defined by the ability | Anytime — on own turn or others' turns |
A practical test: if an ability says "as a bonus action," the bonus action slot is the cost. If an ability says "as a reaction when [condition]," a reaction is the cost and the condition must actually occur. If neither qualifier appears, the ability likely costs an action.
For casters, the D&D frequently asked questions page addresses the Bonus Action spell restriction — one of 5e's more consequential fine-print rules: casting a spell as a bonus action in a round limits action-slot spells to cantrips only for the rest of that turn.
The action economy rewards players who understand which resource each ability draws from before combat begins. A paladin who plans to use Divine Smite, a bonus action spell, and an opportunity attack in the same round will find that at least one of those plans collapses under the weight of a single reaction slot. Knowing the system's hard limits before rolling initiative tends to produce fewer surprised faces mid-encounter — and the broader rules framework makes clear why that planning matters.