Inflection point
point on a continuously differentiable plane curve at which the curve crosses its tangent, that is, the curve changes from being concave to convex, or vice versa
An inflection point is a point on a curve where the curve changes from being concave (going up, then down) to convex (going down, then up), or the other way around.
An undulation point is like an inflection point but the type of curve doesn't change.
