Neutrinos have three mass states, ν₁, ν₂, and ν₃, ordered by their amplitudes in the electron neutrino state, which is a superposition of all three. It is known that m₁<m₂, and that the difference between m₁ and m₃ is much larger than the difference between the first two mass states. This leads to two possibilities for the mass ordering, the "normal ordering" (so called because the order of the masses is the same as the order of the indices we use for the three states, and as the ordering of the masses of the charged leptons most associated with each mass state) where m₃ is the largest mass, and the "inverted ordering" where it is the smallest.

This question is only about the three currently known mass states. If sterile neutrinos exist, that would mean there are more than three mass states, but this market will still resolve according to the ordering of the first three.

See also /JosephNoonan/will-we-know-the-neutrino-mass-orde