A window is an opening in an otherwise solid and opaque surface that allows the passage of light and, if not closed or sealed, air and sound. Windows are usually glazed or covered in some other transparent or translucent material. Windows are held in place by frames, which prevent them from collapsing in.

Etymology

The word Window originates from the Old Norse ‘vindauga', from ‘vindr – wind' and ‘auga – eye'. In Norwegian Nynorsk and Icelandic the Old Norse form has survived to this day (in Icelandic only as a less used synonym to gluggi), while Swedish has kept it—mostly in dialects—as ‘vindöga' (‘öga – eye'). Danish ‘vindue' and Norwegian Bokmål ‘vindu' however, have lost the direct link to ‘eye', just like window has. The Danish (but not the Bokmål) word is pronounced fairly similar to window.

Window is first recorded in the early 13th century, and originally referred to an unglazed hole in a roof. Window replaced the Old English ‘eagþyrl', which literally means ‘eye-hole,' and ‘eagduru' ‘eye-door'. Many Germanic languages however adopted the Latin word ‘fenestra' to describe a window with glass, such as standard Swedish ‘fönster', or German ‘Fenster'. The use of window in English is probably due to the Scandinavian influence on the English language by means of loanwords during the Viking Age. In English the word fenester was used as a parallel until the mid-1700s and fenestration is still used to describe the arrangement of windows within a façade.

Definition and types of windows

A window is an opening in a wall that lets light and possibly air into the room and allows occupants to see out. Primitive windows were just holes. Later, they were covered with animal hide, cloth, or wood. Shutters that could be opened and closed came next. Over time, windows were built that both protected the inhabitants from the elements and transmitted light: mullioned glass windows, which joined multiple small pieces of glass with leading, paper windows, flattened pieces of translucent animal horn, and plates of thinly sliced marble. Mullioned glass windows were the windows of choice among European well-to-do, whereas paper windows were economical and widely used in ancient China , Korea , Japan. In England, glass became common in the windows of ordinary homes only in the early 17th century whereas windows made up of panes of flattened animal hornFact: date=March 2007 were used as early as the 14th century in Northern Britain. Modern-style floor-to-ceiling windows became possible only after the industrial glass making process was perfected. Evidence of glass window panes in Italy dates back nearly 3000 years. Fact: date=December 2007