The term “abatjour” or “abat-jour” is used in several different ways, all of which pertain to light and the deflection of light. The word is lifted directly from the French, and literally means “throw or cast down light,” a reflection of the fact that an abatjour usually directs light in a downward direction for the purpose of creating focused illumination.
One example of an abatjour is a slat or series of slats which are used to create privacy while still allowing light into a room. Screens which serve the same function may also be referred to as abatjours. In this case, the abatjour slants inward so that light falling from the outside is directed into the room and down towards the floor. In this way, a room can have lots of natural light, while the people inside enjoy privacy.
Some of these abatjours are movable, allowing people to take them out of a window when they want an unobstructed view, or when they want to open a window fully for ventilation. They may snap out of their frames, fold back, or swing out to clear the window when someone does not want to have the abatjour in place, as for example when someone is cleaning windows.
The term is also used in reference to a lampshade. Lampshades are designed to focus and direct light to create a pool of light in a specific area for aesthetic reasons or the purpose of disability. Some companies refer to their lampshades as abatjours to add a note of French sophistication to their products, since some people associate French products with luxury or style.
Historically, an abatjour was a window in a large structure with thick walls which had an inward sloping sill. The sloped sill directed more light into the room, allowing the room to be brighter than it would be otherwise. This was extremely useful in structures with slits for windows and other narrow openings to admit light, as rooms might have become oppressive otherwise.
People also refer to skylights as abatjours. Skylights add light to a room by creating a hole in the roof which will admit light as the sun moves across the sky. They enhance privacy as well, since they admit light without giving passerby a view of the inside of a structure. Additionally, they can be useful when structures abut each other, making it impossible to have windows in side walls.