# Stationary Point and Stationary Curve

## Stationary Point and Stationary Curve

A stationary point is a point at which the differential of a function vanishes. A stationary curve is a curve at which the variation of a function vanishes.

For a function of one variable *y = f(x)*, the tangent to the graph of the function at a stationary point is parallel to the *x*-axis. The plane tangent to the surface *z = f(x, y)* at a stationary point of the function of two variables *f(x, y)* is parallel to the *xy*-plane.