If the first derivative of the function $y(x)$, $$\frac{dy}{dx}$$, is the slope at a point and the first indefinite integral $$\int dx y(x)$$ is the area under the curve, then what is the geometric meaning of the second derivative?
$$\frac{d^2y}{dx^2}$$
or the second indefinite integral ?
$$\int dx \int dx y$$
is there some geometric sense in which to understand/interpret the general differential or integral operator?