skylights
One or more horizontal or sloped windows in the roof of a building which let light into the interior.
Skylights are windows in the roof of a building, which admit light into the top floor, the floor below the roof, or an atrium or similar space. Dormer windows (although they are in a roof) do not count as skylights; the glass or other transparent surface must be horizontal or sloped to be considered a skylight.
The transparent surface lies horizontally or on a slope in the roof. Light can enter an occupied room directly below or pass into a taller interior space such as an atrium.
A vertical window in a dormer does not qualify, even though the dormer projects from the roof. A skylight can be openable, but that alone does not make it a retractable roof, which requires movement of a major roof section.