In general, in a theory with several scalar fields, ϕ j, the Nambu–Goldstone mode ϕ g is massless, and parameterises the curve of possible (degenerate) vacuum states. Its hallmark under the broken symmetry transformation is nonvanishing vacuum expectation 〈 δϕ g 〉, an order parameter, for vanishing 〈 ϕ g 〉 = 0, at some ground state |0〉 chosen at the minimum of the potential, 〈∂ V /∂ ϕ i 〉 = 0. In principle the vacuum should be the minimum of the effective potential which takes into account quantum effects, however it is equal to the classical potential to first approximation. Symmetry dictates that all variations of the potential with respect to the fields in all symmetry directions vanish. The vacuum value of the first order variation in any direction vanishes as just seen; while the vacuum value of the second order variation must also vanish, as follows. Vanishing vacuum values of field symmetry transformation increments add no new information.