atrium

noun (plural atria /ˈātrēə/ or atriums)

• 1 Architecture an open-roofed entrance hall or central court in an ancient Roman house.
• a central hall or court in a modern building, with rooms or galleries opening off it, often glass-covered.

• 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 receives oxygenated blood from the pulmonary vein. Also called auricle.