Crystalline solids are distinguished from amorphous solids by the presence of such ordering. While quartz is crystalline silicon dioxode (SiO2), common glass has the same chemical composition but is an amorphous solid. Amorphous solids display some properties of liquids that flow, albeit very slowly. In a household context, crystals (short for lead crystals) refer to glass items made with lead added in the manufacturing process. Despite the confusions with its name, lead crystal or any form of glass is an amorphous solid. Some classify glass as a supercooled liquid.
Liquid crystals occupy a conceptual middle ground between the crystalline and the amorphous--they exhibit order in some dimensions, but amorphous-like disorder in others.