A liquid crystal is a phase of matter that lies between the disorder of liquids and the neatly arranged lattices of crystals. Unlike regular liquids, liquid crystals must have at least one degree of macroscopic order, even if it is only the angular alignment of a nematic.
Liquid crystals lack the full three dimensional position and orientation order of ordinary crystals.
In the isotropic phase, the particles are at random positions and orientations. In the nematic phase, the particles have an overall direction of orientation, but the positions of the individual particles are still random. The direction of alignment is called the director. The nematic order is not perfect and there can be considerable fluctuation about the director. A cholesteric is similar to a nematic, but in a certain direction the director twists about in a helix of a given pitch.