1. One of the four fundamental interactions of nature, which is mediated by photons and acts on quarks and charged leptons. The electromagnetic interaction is weaker than the strong interaction, but stronger than the weak and gravitational interactions. It is associated with electric and magnetic fields and is responsible for atomic structure, chemical reactions, the attractive and repulsive electromagnetic forces associated with electrically charged or magnetically polarized particles, and all other electromagnetic phenomena.

2. An instance of this interaction.