Sample characterized by a (unique) sample axis Z with all directions perpendicular
to Z being equivalent. In other words, the sample properties are invariant
to rotation around Z. Uniaxiality exists in many anisotropic samples and simplifies
the interpretation of their spectra considerably.
PAC, 2007, 79, 293
(Glossary of terms used in photochemistry, 3rd edition (IUPAC Recommendations 2006))
on page 437