This is a bit nitpicky, but so you're aware: the term is differentiable, not derivable. You differentiate a function, you don't derive it.
Em português há uma diferença diminuta de sentido entre "diferenciável" e "derivável" (na Análise Matemática mesmo), mas não recordo mais qual.
O inglês sendo o idioma mutante que é, talvez acabe absorvendo essa diferença de nomenclaturas dessa forma: derivable x differentiable.
That's a linguistic question, not a mathematics one.
In Portuguese there's a very small difference between "differentiable" and "derivable" (in the context of Math Analysis), but I don't recall it.
English being a mutable language, may end up absorbing the difference between nomenclatures in that way (??): derivable x differentiable.