That single (or doubled) convex blade profile is the big defining difference between shears and scissors. There’s some other things like grip sizes and thickness of the blades relative to each other that separate things like tailoring shears and dressmaking shears, but those aren’t nearly as codified. And that’s ignoring all the complexities you get with beauty shears, or the absolute hell that is trying to sharpen pinking or thinning shears, especially if the inner blade has a nick in it that requires reprofiling. Its fascinating how complex such simple tools have become as we’ve adapted them for ever more specialized tasks!