1) Calculation 2) Computation 3) Figuring 4) Reckoning 1) Distinguishable 
[adj] - possessing a differential coefficient or derivative 2. [adj] - capable of being perceived as different
A function is said to be differentiable at a point when the function's derivative exists at that point. A function will fail to be differentiable at places where the function is not continuous or where the function has corners.
adjective capable of being perceived as different; `differentiable species`
capable of being differentiated.