In classical architecture, hypaethral describes a building with no roof and with columns forming a partial wall.
The term originates from Latin hypaethrus, from Ancient Greek ὕπαιθρος hupaithros ὑπό hupo- "under" and αἰθήρ aither "sky, air". It was described by the Roman architect Vitruvius in his treatise De architectura, written for the emperor Caesar Augustus probably about 15 BC.