[glas, glahs] 
| 1. | Carter, 1858–1946, U.S. statesman. |
| 2. | Philip, born 1937, U.S. composer. |
glass (glās)
n.
Any of a large class of materials with highly variable mechanical and optical properties that solidify from the molten state without crystallization, are typically made by silicates fusing with boric oxide, aluminum oxide, or phosphorus pentoxide, are generally hard, brittle, and transparent or translucent, and are considered to be supercooled liquids rather than true solids.
Something usually made of glass, such as a window, mirror, drinking vessel.
glasses A pair of lenses mounted in a light frame, used to correct faulty vision or protect the eyes. Also called spectacles.
A device, such as a monocle or spyglass, containing a lens or lenses and used as an aid to vision.
| glass (glās) Pronunciation Key
A usually transparent or translucent material that has no crystalline structure yet behaves like a solid. Common glass is generally composed of a silicate (such as silicon oxide, or quartz) combined with an alkali and sometimes other substances. The glass used in windows and windshields, called soda glass, is made by melting a silicate with sodium carbonate (soda) and calcium oxide (lime). Other types of glass are made by adding other chemical compounds. Adding boron oxide causes some silicon atoms to be replaced by boron atoms, resulting in a tougher glass that remains solid at high temperatures, used for cooking utensils and scientific apparatuses. Glass used for decorative purposes often has iron in it to alter its optical properties. Our Living Language : Common sand and glass are both made primarily of silicon and oxygen, yet sand is opaque and glass is transparent. Glass owes its transparency partly to the fact that it is not a typical solid. On the molecular level, solids usually have a highly regular, three-dimensional crystalline structure; the regularities distributed throughout the solid act as mirrors that scatter incoming light. Glass, however, consists of molecules which, though relatively motionless like a typical solid, are not arranged in regular patterns and thus exhibit little scattering; light passes directly through. At a specific temperature, called the melting point, the intermolecular forces holding together the components of a typical solid can no longer maintain the regular structure, which then breaks down, and the material undergoes a phase transition from solid to liquid. The phase transition in glass, however, depends on how quickly the glass is heated (or how quickly it cools), due to its irregular solid structure. |