The function describing the variation of plastic anisotropy r at the uniaxial deformation ε is a compendium of knowledge on polycrystalline metals subdued to plastic working. In real single crystals r(ε) function characterizes the degree of imperfection of the crystallographic orientation (“texture of a single crystal”). It has been shown that the best fitting function of the r-ε relationship for single crystals as well as for polycrystalline metals is that based on a hyperbolic function.