In searching for a suitable translation of 'indistinguishable', I found the French word 'indifférenciable'. http://www.wordreference.com/enfr/indistinguishable
From my point of view, as an Anglophone, I wonder something when comparing this French word to English 'indifferentiable' (some would argue this isn't a word, but the colloquial meaning is "unable to differentiate"). I wonder if 'indifférenciable' also carries the meaning "Unable to to differentiate", not only in the sense of comparing differences, but also in the sense of derivatives and differentiation in the world of calculus.
Can the word 'indifférenciable' imply 'unable to derive or differentiate' in the context of calculus?