How about we have this thing called science, physics in this case as applied to structural engineering and material science.
In engineering deflection is the degree to which a structural element is displaced under a load.
It also falls under a number of stress moduli
Modulus of Elasticity “young’s modulus”
(How much load till it bends)
Modulus of Rupture
(how much side load till it breaks)
Elasticia (the theoretical shape of a flexible object) such as the exact curve of deformation m, maximum tip displacement, maximum tip deflection angle, distribution of curvature, and distribution of bending moment has all been described since the 17th century by Euler-Bernoulli’s beam equations.
As far as stiffness being confusing for its association with bendiness and whippyness
real scientific terms there.
The Stiffness main factor is the taper, the closer it is to a true cone the stiffer it will be.
Bendiness main factor is little to no taper
Whippy is from the same lack to no taper plus a nodal point closer to the center of the cue. So it flops around like a fish out the water.
Inverted tapers/ parabolic are another method of nodal shifting.
But anyway I digress
Shafts deflect, just like steel beams or beams of light, moving objects don’t deflect into motion, they get deflected off course while in motion.
Like the one that cracked into mine and bounced over the fence for a auto double
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