Solids having a regular periodic arrangement of atoms or molecules. But Amorphous solids have disordered arrangement in their atoms or molecules like gases. Even though atoms or molecules have disordered, they have fixed positions so they cannot move like gases molecules and amorphous solids show rigidity to move due to molecular attractions. So these amorphous solids not having a fixed structure like solids and not having free movement like gases. That is why we can call these amorphous solids as supercooled liquids of high density and viscosity.