“A glass is a nonequilibrium state of matter between that of a solid and a liquid. It is a non-crystalline amorphous solid that has a nanoscopically and microscopically disordered structure but many of the mechanical properties of a solid. Glass is a nonequilibrium, non-crystalline state of matter that appears solid on a short time scale but continuously relaxes towards the liquid state . . . . a nonequilibrium, non-crystalline condensed state of matter that exhibits a glass transition. The structure of glasses is similar to that of their parent supercooled liquids, and they spontaneously relax toward the supercooled liquid state. Their ultimate fate, in the limit of infinite time, is to crystallize. In the glassy state, the viscosity is exceptionally high, conformational changes are severely inhibited, and the material is metastably trapped in a solid but microscopically disordered state. A glass is rigid and brittle.” – Martin Chaplin, Water Structure and Science (internal quotes and citations omitted)