\kappaThe Greek letter kappa (\kappa) is commonly used in mathematics and science to represent various concepts, such as curvature, condition number, or thermal conductivity, depending on the context.
Curvature of a curve, where R is the radius of curvature.
\kappa = \frac{1}{R}Condition number of a matrix A, used in numerical analysis.
\kappa(A) = \|A\| \|A^{-1}\|Fourier's law of heat conduction, where \kappa is the thermal conductivity.
q = -\kappa \nabla T