Amorphous solids are solid substances that lack a defined shape, that is, the opposite of crystalline solids. Unlike crystals, the atoms/molecules of amorphous solids are not arranged in a repeating, defined pattern, ie. they have a short range order, where a regular and periodically repeating pattern is observed over short distances only. Examples include glass and wax. Crystalline solids have a sharp melting point but amorphous solids soften over a range of temperatures and can be easily molded and shaped. Amorphous solids have a tendency to flow, though very slowly. Therefore, sometimes these are called pseudo solids or super cooled liquids. Glass windows, for example, become slightly thicker at the bottom than the rest over a long period of time because glass moves downwards slowly.