Glass is an amorphous solid, usually transparent, and has a wide range of practical, technical and decorative applications in fields such as window glass, tableware and optoelectronics. The most familiar and oldest type of glass in history is "silicate glass", which is based on the chemical component silica (silica or quartz), which is the main component of sand.

In science, the term "glass" is generally defined in a broad sense, including all solids that have an amorphous (i.e., amorphous) structure at the atomic scale and exhibit a glassy transition when heated to a liquid state. Porcelain and many polymer thermoplastics used in daily life are glass. This type of glass can be made from materials completely different from silica: metal alloys, ionic melts, aqueous solutions, molecular liquids and polymers.