Negative energy can refer to several concepts:
- Energy in any system below an arbitrarily defined level (called reference level, ground state, or zero level). Examples include electron potential energy within an atom under the Bohr model of atomic structure, and gravitational potential energy in Newton's model of gravity.
- Energy in any system below the conventionally-defined ground state. Examples are positrons under the Dirac sea model of electron behavior, and the region of reduced vacuum energy associated with the Casimir effect. This type of effect typically occurs under exotic or unexpected conditions, as the definition of the ground state is usually chosen because it is the state of lowest expected energy within a system.
- Negative rest energy, which corresponds to negative mass, which has many unusual physical consequences.
- In the roleplaying game Dungeons & Dragons, negative energy is usually associated with evil and death, and undead beings such as zombies, ghosts, and wraiths are animated by negative energy. It is considered the be the opposite of life (positive) energy, and contact with negative energy by a living being is similar to a heated (positive) object touching a cool (negative) object, with the negative energy 'draining' the life energy from the creature.
