atrium

noun (plural atria /ˈeɪtrɪə/ or atriums)

• 1 Architecture an open-roofed entrance hall or central court in an ancient Roman house.
• a central hall in a modern building, typically rising through several stories and having a glazed roof.
• the forecourt of a large church built on the basilican plan.

• 2 Anatomy each of the two upper cavities of the heart from which blood is passed to the ventricles. The right atrium receives deoxygenated blood from the veins of the body, the left atrium oxygenated blood from the pulmonary vein. Also called auricle.