n. pl. a·tri·a (ātrē-ə) or a·tri·ums
1. Architecture A rectangular court, as:
a. A usually skylit central area, often containing plants, in some modern buildings, especially of a public or commercial nature.
b. The open area in the center of an ancient Roman house.
c. The forecourt of a building, such as an early Christian church, enclosed on three or four sides with porticoes.
2. Anatomy A body cavity or chamber, especially either of the upper chambers of the heart that receives blood from the veins and forces it into a ventricle. Also called auricle.
[Latin ātrium; see āter- in the Appendix of Indo-European roots.]
The American Heritage® Dictionary of the English Language, Fifth Edition copyright ©2020 by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
Indo-European & Semitic Roots Appendices
Thousands of entries in the dictionary include etymologies that trace their origins back to reconstructed proto-languages. You can obtain more information about these forms in our online appendices:
The Indo-European appendix covers nearly half of the Indo-European roots that have left their mark on English words. A more complete treatment of Indo-European roots and the English words derived from them is available in our Dictionary of Indo-European Roots.