A row of windows set high in a wall, especially in a church, that allows light into the central part of a building; also spelled clerestory.
From Middle English cler (clear) plus story (a row or tier of windows). Architectural term from medieval period, where 'clear' meant 'letting light through' and 'story' meant a horizontal section of a building.
Medieval architects used clearstories as a brilliant engineering hack—they'd build arches and vaults below but then poke windows way up high above the roof of side aisles, bathing the whole center in light. It's one of the most elegant solutions to a practical problem in architecture.
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