[This list is incomplete, I'm taking it one letter at a time, and going back in to add links as I create relevant pages.]
- aberrant [origin]: Aberrant creatures are native to or shaped by the Far Realm.
- acid [keyword]: A damage type.
- adventurer: The character controlled by a player other than the Dungeon Master. An adventurer is sometimes called a player character.
- air [keyword]: An air creature is strongly connected to the element of air.
- angel [keyword]: Angels are immortal creatures native to the Astral Sea. They don't need to breathe, eat, or sleep.
- animate [type]: Animate creatures are given life through magic. They don't need to breathe, eat, or sleep.
- augmentable [keyword]: An effect type. A power that has the augmentable keyword has optional augmentations, which a character can use at the cost of power points. Only certain characters have such points.
- aquatic [keyword]: Aquatic creatures can breathe underwater. In aquatic combat, an aquatic creature gains a +2 bonus on attack rolls against non-aquatic creatures.
- area of effect: An area of a specific size where a particular effect takes place. An area of effect usually has one of three types: blast, burst, or wall. Area powers and close powers almost always involve an area of effect.
- aura [keyword]: An effect type. An aura is a continuous effect that emanates from a creature.