skylight; dormer window; transom
A window installed primarily to let in light, often placed high on a wall, in a roof, or above a door. Covers skylights, dormer windows, and transom windows.
We installed a skylight in the roof to brighten the room.
Soft light is coming in through the transom window in the hallway.
Standard kanji spelling using 明かり (light) and 窓 (window).
Variant spelling with 明り instead of 明かり; less common but still seen.
Compound of 明かり (light) and 窓 (window). The exact historical derivation is uncertain, but the word transparently describes a window for letting in light.