A roshandan (Hindi/Urdu: रोशनदान or روشندان) is a feature of many dwelling structures in North India and Pakistan that is a combined skylight and ventilating window.[1][2] Roshandans are usually located high on a room's walls, and often on top of windows. They are essentially smaller windows that swivel open when needed. Smaller roshandans are sometimes called roshandanis. The high location of roshandans means that, for part of the summer (except for the months when the Loo winds blow in the region), they can be kept open to allow heated air just below the ceiling to escape while retaining relatively cooler air inside.[2] In wintertime, they are kept shut and used purely as skylights.
The term roshandan literally means "that which has/admits light" in several Indo-Aryan languages, derived from Persian.[3] Though the word roshandan is often translated to ventilator in English in the Indian subcontinent, this is incorrect literally speaking.[3]
... The bungalow was a typical north Indian one, with a large central room lit only by skylights (roshandans) and a number of others opening out from them ...
... Thirdly, while obviating direct sunlight, it had to allow some light and air to enter through overhead roshandans ...
... Roshandan means, -'that which has light'. The translation in English of such an architectural feature is usually 'ventilator'. ... Therefore the correct name for this oriental architectural feature is 'Roshandan' and not ventilator ...