Category:Atrium

A"tri*um, n.; pl. Atria. Etym: [L., the fore court of a Roman house.]

1. (Arch.) (a) A square hall lighted from above, into which rooms open at one or more levels. (b) An open court with a porch or gallery around three or more sides; especially at the entrance of a basilica or other church. The name was extended in the Middle Ages to the open churchyard or cemetery.

2. (Anat.)

Defn: The main part of either auricle of the heart as distinct from the auricular appendix. Also, the whole articular portion of the heart.

3. (Zoöl.)

Defn: A cavity in ascidians into which the intestine and generative ducts open, and which also receives the water from the gills. See Ascidioidea.