Electromagnetism is the branch of science concerned with the forces that occur between electrically charged particles. In electromagnetic theory these forces are explained using electromagnetic fields. The electromagnetic force is one of the four fundamental interactions in nature, the other three being the strong interaction, the weak interaction and gravitation.
The word is a compound from two Greek terms, ἢλεκτρον, ēlektron, "amber" (as electrostatic phenomena were first described as properties of amber by the philosopher Thales), and μαγνήτης, magnētēs, "magnet" (the magnetic stones found in antiquity in the vicinity of the Greek city of Magnesia, in Lydia, Asia Minor).
Electromagnetism is the interaction responsible for almost all the phenomena encountered in daily life, with the exception of gravity. Ordinary matter takes its form as a result of intermolecular forces between individual molecules in matter. Electrons are bound by electromagnetic wave mechanics into orbitals around atomic nuclei to form atoms, which are the building blocks of molecules. This governs the processes involved in chemistry, which arise from interactions between the electrons of neighboring atoms, which are in turn determined by the interaction between electromagnetic force and the momentum of the electrons.