Electromagnetism may refer to any of the following:
1. The science of electricity and magnetism; specifically, the study of electric and magnetic fields. The two fields are in fact different manifestations of the same physical field, and are interconverted according to the speed of the observer. The theory of electromagnetism, including light, was first developed by Michael Faraday and James Clerk Maxwell in the 19th century. See also Maxwell's equation.
2. Magnetism arising from a moving electric charge.
3. One of the four fundamental forces of nature along with gravity, the weak force, and the strong force. It is the interaction due to electric charge, which also includes magnetic effects that have to do with moving electric charges. Electromagnetism is the second strongest force after the strong force. At the quantum level it is mediated by photons, and is well described by the theory of quantum electrodynamics.