Hi, With respect to derivative notation... d/dx(y) //1st derivative of y w.r.t x d/dx (dy/dx) = d^2y/dx^2 //2nd derivative d/x (d^2y/dx^2) = d^3y/dx^3 //3rd derivative If you continue finding derivatives in this way, why do the d's increment in the numerator and not in the denominator while the x's increment in the denominator? I understand the pattern and even intuitively it makes sense to read: d^2y/dx^2 as the second derivative of y w.r.t x, but I don't understand why the notation behaves this way. *The formatting changed when I posted. The "//" means comment. Thanks!