Often formed by concentrated systems of
surfactants. These are states of matter in which
anisometric molecules (or particles) are regularly arranged in one (nematic state) or two (
smectic state) directions, but randomly arranged in the remaining direction(s).
Source:
PAC, 1972, 31, 577
(Manual of Symbols and Terminology for Physicochemical Quantities and Units, Appendix
II: Definitions, Terminology and Symbols in Colloid and Surface Chemistry)
on page 613