gauge invariance

(electromagnetism) The invariance of electric and magnetic fields and electrodynamic interactions under gauge transformations.
(physics) The invariance of any field theory under gauge transformations.
(quantum mechanics) An invariance of a Lagrangian based on an internal gauge group, such as U(1) for electromagnetism or U(1) × SU(2) for the Weinberg-Salam unified model of weak and electromagnetic interactions.