of fluorescence emitted by samples excited with plane-polarized light. When a fluorophore absorbs polarized light, it may rotate before re-emitting a photon, and anisotropy measurements reveal the average angular displacement that occurs between absorption and emission. This makes fluorescence anisotropy a useful tool for determining the shape of a macromolecule or studying its local molecular mobility.

In NMR spectroscopy, the orientation of nuclei with respect to the