[ ey-tree-uh m ]
/ ˈeɪ tri əm /

noun, plural a·tri·a [ey-tree-uh] /ˈeɪ tri ə/, a·tri·ums.

  1. 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.
  2. a courtyard, flanked or surrounded by porticoes, in front of an early or medieval Christian church.
  3. 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 forms

a·tri·al, adjectivein·ter·a·tri·al, adjective Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019

Examples from the Web for atrium

British Dictionary definitions for atrium


/ (ˈeɪtrɪəm, ˈɑː-) /

noun plural atria (ˈeɪtrɪə, ˈɑː-)

the open main court of a Roman house
a central often glass-roofed hall that extends through several storeys in a building, such as a shopping centre or hotel
a court in front of an early Christian or medieval church, esp one flanked by colonnades
anatomy a cavity or chamber in the body, esp the upper chamber of each half of the heart

Derived Forms

atrial, adjective

Word Origin for atrium

C17: from Latin; related to āter black, perhaps originally referring to the part of the house that was blackened by smoke from the hearth
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Medicine definitions for atrium


[ ātrē-əm ]

n. pl. a•tri•ums

A chamber or cavity to which several chambers or passageways are connected.
Either the right or the left upper chamber of the heart that receives blood from the veins and forces it into a ventricle.
That part of the tympanic cavity that lies below the eardrum.
A subdivision of the alveolar duct in the lung from which the alveolar sacs open.
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.

Science definitions for atrium


[ ātrē-əm ]

Plural atria atriums

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.
The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.