Non-relativistic quantum electrodynamics
Non-relativistic quantum electrodynamics (NRQED) is a low-energy approximation of quantum electrodynamics which describes the interaction of (non-relativistic, i.e. moving at speeds much smaller than the speed of light) spin one-half particles (e.g., electrons) with the quantized electromagnetic field.
Source: Wikipedia — Non-relativistic quantum electrodynamics (CC BY-SA 4.0)