Neutrino-nucleus elastic scattering (νAel) provides a unique laboratory to study the quantum-mechanical (QM) coherency effects in electroweak interactions. The deviations of the cross sections from those of completely coherent systems can be quantitatively characterized through a coherency parameter α (q2). The relations between α and the underlying nuclear physics in terms of nuclear form factors are derived. The dependence of cross section on α (q2) for the various neutrino sources is presented. The α (q2) values are evaluated from the measured data of the COHERENT CsI and Ar experiments. Complete coherency and decoherency conditions are excluded by the CsI data with p = 0.004 at q2 = 3.1 × 103 MeV2 and p = 0.016 at q2 = 2.3 × 103 MeV2, respectively, verifying that both QM superpositions and nuclear many-body effects contribute to νAel interactions.