The QCD Lagrangian is invariant under local SU(3) gauge transformations; i.e., transformations of the form ψ ψ → → ψ ψ ′ = U ψ ψ , where U = e − − i g s λ λ a ϕ ϕ a ( x ) is 3 × × 3 unitary matrix with determinant 1, making it a member of the group SU(3), and ϕ ϕ a ( x ) is an arbitrary function of spacetime.