Fanlight
Part of speech: noun
Definition: a semicircular or semi-oval window over a door or other window, normally having a fan-like structure of ribs; sometimes hinged to the transom
Skylight
Part of speech: noun
Definition: A window, dome, or opening in the roof or ceiling, to admit natural light.Diffuse sky radiation—solar radiation reaching the earth's surface after having been scattered from the direct solar beam by molecules or suspensoids in the atmosphere