- A material whose properties are intermediate between those of a crystal and a liquid. The constituent particles tend to arrange themselves with much greater order than an ordinary liquid, but not enough to become solid crystals, When subjected to variations in a surrounding electric field, its optical properties change. For example, a small applied electrical signal may darken such a crystal, enabling it to be differentiated from a light-colored background, making them suitable for displays. Certain liquid crystals vary, depending on the temperature, the color of the light they reflect, and can be used as thermometers. Its abbreviation is LC.