Editing Non-uniform rational B-spline (section)

=== Order ===
The ''order'' of a NURBS curve defines the number of nearby control points that influence any given point on the curve.  The curve is represented mathematically by a polynomial of degree one less than the order of the curve.  Hence, second-order curves (which are represented by linear polynomials) are called linear curves, third-order curves are called quadratic curves, and fourth-order curves are called cubic curves.  The number of control points must be greater than or equal to the order of the curve.

In practice, cubic curves are the ones most commonly used.  Fifth- and sixth-order curves are sometimes useful, especially for obtaining continuous higher order derivatives, but curves of higher orders are practically never used because they lead to internal numerical problems and tend to require disproportionately large calculation times.