Fluorescence polarization is synonymous with fluorescence anisotropy. A magnetic particle with uniaxial anisotropy has one easy axis. This is called birefringence or optical anisotropy. Many crystals are anisotropic to light ("optical anisotropy"), and exhibit properties such as birefringence. This applies to a particle with uniaxial magnetocrystalline anisotropy. The anisotropy of such crystals is called "uniaxial anisotropy". Macroscopic structure can be adjusted to compensate for this anisotropy. However, performance is plagued by poor conductivity and crystal anisotropy. Small spherical particles will show no angular dependence, hence no anisotropy. A torque is thus a measure of the sample's magnetic or shape anisotropy. The observed magnetic anisotropy in an object can happen for several different reasons. Steady-state fluorescence anisotropy only give an "average" anisotropy. It is a special case of magnetic anisotropy. The anisotropy ratio is a value computed to compare elastic anisotropy in materials. This is a form of magnetic anisotropy called "shape anisotropy".