Fanlight (noun)

1. A semi-circular or fan-shaped window above a door or window, usually with decorative glazing bars.
2. A light or ventilator in the form of a fan or semi-circle.

Origin:

Early 19th century; earliest use found in the london magazine. from fan + -light.

Examples:

1. The fanlight above the door let in a shaft of light.
2. The elegant fanlight gave the room a sophisticated touch.
3. He peered through the fanlight and saw nobody inside.
4. The fanlight was used to ventilate the room and let in natural light.
5. The fanlight was made of stained glass, adding color and interest to the room.