differentiable
Mathematical term used in calculus to describe a function that has a derivative at a given point.
この関数はすべての点で微分可能です。
This function is differentiable at every point.
微分 is the noun 'differentiation' or 'differential', while 微分可能 is the adjective 'differentiable'.
infinitely differentiable
Compound of 微分 (differentiation) and 可能 (possible).