What is "quarter glass"

n. (context vehicles English) the small triangular-shaped side window on some vehicles.

Quarter glass or quarter light on automobiles and closed carriages may be a side window in the front door or located on each side of the car just forward of the rear window of the vehicle. Only some cars have them. In some cases the fixed quarter glass may set in the corner or "C- pillar" of the vehicle. Quarter glass is also sometimes called a valence window.

This window may be set on hinges and is then also known as a vent window. Most often found on older vehicles on the front door, it is a small roughly triangular glass in front of and separate from the main window that rotates inward (see top right image) for ventilation.