Glass generally refers to hard, brittle, transparent material, such as those used for windows, manybottles, or eyewear. Examples of such materials include, but are not limited to, soda-lime glass,borosilicate glass, acrylic glass, sugar glass, isinglass (Muscovy-glass), or aluminium oxynitride. In the technical sense, glass is an inorganic product of fusion which has been cooled to a rigid condition without crystallizing. Many glasses contain silica as their main component and glass former.