  By employing the gradient/Wilson flow, we derive a universal formula that
expresses a correctly normalized flavor non-singlet axial-vector current of
quarks. The formula is universal in the sense that it holds independently of
regularization and especially holds with lattice regularization. It is also
confirmed that, in the lowest non-trivial order of perturbation theory, the
triangle diagram containing the formula and two flavor non-singlet vector
currents possesses non-local structure that is compatible with the triangle
anomaly.
