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gauge invariance[′gāj in′ver·ē·əns]
The invariance of electric and magnetic fields and electrodynamic interactions under gauge transformations.
The invariance of any field theory under gauge transformations.
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.