The OED definition is "Best, most favourable, esp. under a particular set of circumstances". So it really is not the degree of goodness or bestness, but the ab

The OED definition is "Best, most favourable, esp. under a particular set of circumstances". So it really is not the degree of goodness or bestness, but the absolute best. Again, like uniqueness, a boolean property. This is only important to me because I'm a scientist/engineer. If I claim my system performs optimally, this is a big claim and needs proof, since I'm claiming it could not possibly be better. Since I have to be so careful in technical writing, my spider-sense tingles when I see technical terms used with an almost-but-not-exactly correct meaning. YMMV.