The rule which rules definition is this: definition is a function of equal and opposite  relativity.

mgH = hf

when wavelength = amplitude of a wave.
makes sense. the down equals the up.

which is to say that relativity is equal and opposite.

e=mc2 = 1/2mv2. (asimov)

SO THE EQUIValence applies to quantum level and explains how we get mass.

when wavelength equals amplitude, mass has an equivalence to h/λv.

E = (h/λv)c2; 

So, dividing by c2  gives us mass when λ = H, where H is amplitude.