Definition
Let be a Unit Tangent Vector of a smooth curve, be the Principal Unit Normal Vector, and be the Binormal Vector
\frac{d\mathbf{T}}{ds} &= \kappa \mathbf{N}\\ \frac{d\mathbf{N}}{ds} &= -\kappa \mathbf{T} + \tau\mathbf{B}\\ \frac{d\mathbf{B}}{ds} &= \tau \mathbf{N} \end{aligned}$$ where $\kappa$ is the [[Curvature of Curves]] and $\tau$ is the [[Torsion of Curves]]