List of Symbols.
 a geometrical dimension, [m] A geometrical dimension, [m] b geometrical dimension, [m] B Biot number, usually hL/k. cp specific heat, [J/kg/K] dsi differential area element on surface Si, [m2] differential volume element, [m3] erf (z) error function, f boundary function, units [K] for type 1 boundary, otherwise units  [W/m2] F(r) initial temperature distribution, [K] g volume energy generation, G Green's function h heat transfer coefficient, [W/m2/K] H(t) Heaviside unit step function i,j indices J Joule, unit of energy k thermal conductivity [W/m/K] kg kilogram, unit of mass K Kelvin, unit of absolute temperature L geometrical dimension, sometimes body thickness, [m] m fin effect parameter, [m-1]; also meter, unit of length ni outward unit normal vector on surface Si P propagator, function related to the GF q heat flux, [W/m2] r radial coordinate, [m] position vector, [m] R numbering system designation for radial cylindrical coordinate RS numbering system designation for radial spherical coordinate Si body surface sec second, unit of time t time, [sec] T temperature, [K] x,y,z Cartesian coordinates X, Y, Z numbering system designations for Cartesian coordinates W Watt, a unit of power, equal to one Joule per second.

Greek symbols

 thermal diffusivity eigen value Dirac delta function Laplacian, spatial derivative in Heat equation small parameter density [kg/m3] time at which the heat pulse is released, [sec] azimuthal angle, cylindrical and spherical coordinates polar angle, spherical coordinates