Damage

Damage, or DMG, is a reduction in health or an action that reduces health from an attack. For example, a weapon attack or spell attack that reduces the health of the target is damage, but losing a health boosting buff is not considered damage.

Losing mana from an attack can also be considered damage, but generally is not referred to in that way since reducing mana to 0 (zero) will not cause death; nor do spells interrupt casting or other actions prone to damage, such as First Aid.