noun,plurala·tri·a[ey-tree-uh]/ˈeɪ tri ə/, a·tri·ums.
Architecture.
Also called cavaedium.the main or central room of an ancient Roman house, open to the sky at the center and usually having a pool for the collection of rain water.
a courtyard, flanked or surrounded by porticoes, in front of an early or medieval Christian church.
a skylit central court in a contemporary building or house.
Anatomy. either of the two upper chambers on each side of the heart that receive blood from the veins and in turn force it into the ventricles.
Origin of atrium
1570–80; < Latin (in anatomical sense < NL)
Related formsa·tri·al, adjectivein·ter·a·tri·al, adjective
1570s, from Latin atrium "central court or main room of an ancient Roman house, room which contains the hearth," sometimes said (on authority of Varro, "De Lingua Latina") to be an Etruscan word, but perhaps from PIE *ater- "fire," on notion of "place where smoke from the hearth escapes" (through a hole in the roof). Anatomical sense of "either of the upper cavities of the heart" first recorded 1870. Meaning "skylit central court in a public building" first attested 1967.
A chamber of the heart that receives blood from the veins and forces it by muscular contraction into a ventricle. Mammals, birds, reptiles, and amphibians have two atria; fish have one.
Inside the Washington Navy Yard’s Building 197 During Alexis’s Rampage