In the context of physical sciences, several forms of energy have been defined. These include:
- Thermal energy, thermal energy in transit is called heat
- Chemical energy
- Electric energy
- Radiant energy, the energy of electromagnetic radiation
- Nuclear energy
- Magnetic energy
- Elastic energy
- Sound energy
- Mechanical energy
- Luminous energy
- Mass (E=mc²)
These forms of energy may be divided into two main groups; kinetic energy and potential energy. Other familiar types of energy are a varying mix of both potential and kinetic energy.
Energy may be transformed between these forms, some with 100% energy conversion efficiency and others with less. Items that transform between these forms are called transducers.
The above list of the known possible forms of energy is not necessarily complete. Whenever physical scientists discover that a certain phenomenon appears to violate the law of energy conservation, new forms may be added, as is the case with dark energy, a hypothetical form of energy that permeates all of space and tends to increase the rate of expansion of the universe.