heat under the ground used to heat water and make steam to turn generator turbines and make electricity.

(physics) The energy needed to separate the constituent parts of an atom or nucleus; equivalent to the mass defect.

(physics) The energy released by a nuclear reaction; either through nuclear fission or nuclear fusion / Such energy used as a power source.

Energy in the form of electromagnetic radiation emitted from the Sun; especially that part of this energy that is converted into usable thermal or electrical energy by man.

(physics) The sum of the potential energy and kinetic energy of a body or system

(chemistry, physics) The energy required to initiate a reaction. For example, the flame from the fuse of a firecracker provides a small initial amount of energy, after which the explosive reaction proceeds by itself, releasing a considerably larger quantity of energy. A small push given to a stable but top-heavy object may cause it to fall over; the potential energy released during the fall was present in the system all along but could not be realized as long as the object was upright and balanced.

(astronomy, astrophysics) A hypothetical form of energy which, it is supposed, is spread uniformly throughout space (and time) and has anti-gravitational properties: it represents a possible mechanism for the cosmological constant, and thus is one of the possible explanations for the current accelerating rate of expansion of the universe; and it is estimated to account for about 74% of the mass-energy of the universe.

(physics) The underlying background energy of empty space associated with constant vacuum fluctuations.

(physics) Energy stored in a ferromagnetic material as a result of the work done by the rotation of its magnetization

The energy of a system with respect to its centre of gravity