In physics, electromagnetism is an interaction that occurs between particles with electric charge via electromagnetic fields. The electromagnetic force is one of the four fundamental forces of nature. It is the dominant force in the interactions of atoms and molecules. Electromagnetism describes and relates the three distinct but closely intertwined phenomena of electricity, magnetism, and optics. In the study of electromagnetism these phenomena are described by the 3 sub-disciplines: electrostatics, magnetostatics, and electrodynamics.