System Reference Document 5.2.1
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Area of Effect
The descriptions of many spells and other features 
specify that they have an area of effect, which typ -
ically has one of six shapes. These shapes are de -
fined elsewhere in this glossary:
Cone
Cube
Cylinder
Emanation
Line
Sphere
An area of effect has a point of origin, a location 
from which the effect’s energy erupts. The rules for 
each shape specify how to position its point of ori -
gin. If all straight lines extending from the point of 
origin to a location in the area of effect are blocked, 
that location isn’t included in the area of effect. 
To block a line, an obstruction must provide Total 
Cover. See also “Cover.”
 If the creator of an area of effect places it at an 
unseen point and an obstruction—such as a wall—
is between the creator and that point, the point 
of origin comes into being on the near side of the 
obstruction.
Armor Class
An Armor Class (AC) is the target number for an 
attack roll. AC represents how difficult it is to hit a 
target.
 Your base AC calculation is 10 plus your Dexterity 
modifier. If a rule gives you another base AC calcula-
tion, you choose which calculation to use; you can’t 
use more than one. See also  “Attack Roll.”
Armor Training
Armor training allows you to use armor of a certain 
category without the following drawbacks. If you 
wear Light, Medium, or Heavy armor and lack train -
ing with it, you have Disadvantage on any D20 Test 
that involves Strength or Dexterity, and you can’t 
cast spells. If you use a Shield and lack training with 
it, you don’t gain its AC bonus. See also  “Disadvan-
tage” and “Equipment” (“Armor”).
Attack [Action]
When you take the Attack action, you can make one 
attack roll with a weapon or an Unarmed Strike.
 Equipping and Unequipping Weapons. You can 
either equip or unequip one weapon when you make 
an attack as part of this action. You do so either 
before or after the attack. If you equip a weapon 
before an attack, you don’t need to use it for that at -
tack. Equipping a weapon includes drawing it from 
a sheath or picking it up. Unequipping a weapon in -
cludes sheathing, stowing, or dropping it.
 Moving between Attacks. If you move on your 
turn and have a feature, such as Extra Attack, that 
gives you more than one attack as part of the Attack 
action, you can use some or all of that movement to 
move between those attacks.
Attack Roll
An attack roll is a D20 Test that represents making 
an attack with a weapon, an Unarmed Strike, or a 
spell. See also “Playing the Game” (“D20 Tests”).
Attitude
A monster has a starting attitude toward a player 
character: Friendly, Hostile, or Indifferent. See also  
“Friendly,” “Hostile,” “Indifferent,” and “Influence.”
Attunement
Some magic items require a creature to form a 
bond—called Attunement—with them before the 
creature can use an item’s magical properties. A 
creature can have Attunement with no more than 
three magic items at a time. See also  “Equipment” 
(“Magic Items”).
Blinded [Condition]
While you have the Blinded condition, you experi -
ence the following effects.
 Can’t See. You can’t see and automatically fail any 
ability check that requires sight.
 Attacks Affected.  Attack rolls against you have 
Advantage, and your attack rolls have Disadvantage.
Blindsight
If you have Blindsight, you can see within a specific 
range without relying on physical sight. Within that 
range, you can see anything that isn’t behind Total 
Cover even if you have the Blinded condition or are 
in Darkness. Moreover, in that range, you can see 
something that has the Invisible condition.
Bloodied
A creature is Bloodied while it has half its Hit Points 
or fewer remaining.
Bonus Action
A Bonus Action is a special action that you can take 
on the same turn that you take an action. You can’t 
take more than one Bonus Action on a turn, and you 
have a Bonus Action to take only if a rule explicitly 
says so. See also “Playing the Game” (“Actions”).
Breaking Objects
Objects can be harmed by attacks and by some 
spells, using the rules below. If an object is exceed -
ingly fragile, the GM may allow a creature to break 
it automatically with the Attack or Utilize action.
 Armor Class. The Object Armor Class table sug -
gests ACs for various substances.