  We introduce the idea of Form Dominance in the (type I) see-saw mechanism,
according to which a particular right-handed neutrino mass eigenstate is
associated with a particular physical neutrino mass eigenstate, leading to a
form diagonalizable effective neutrino mass matrix. Form Dominance, which
allows an arbitrary neutrino mass spectrum, may be regarded as a generalization
of Constrained Sequential Dominance which only allows strongly hierarchical
neutrino masses. We consider alternative implementations of the see-saw
mechanism in minimal A4 see-saw models and show that such models satisfy Form
Dominance, leading to neutrino mass sum rules which predict closely spaced
neutrino masses with a normal or inverted neutrino mass ordering. To avoid the
partial cancellations inherent in such models we propose Natural Form
Dominance, in which a different flavon is associated with each physical
neutrino mass eigenstate.
