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[ey-tree-uh m] /ˈeɪ tri əm/
noun, plural atria
[ey-tree-uh] /ˈeɪ tri ə/ (Show IPA),
  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
atrial, adjective
interatrial, adjective Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2015.
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Examples from the web for atria
  • In a healthy heart, electrically conductive muscle cells fire for each contraction of the atria and ventricles.
  • The atria are receiving chambers, and the ventricles distributing ones.
  • When the atria stop contracting smoothly, pools of blood can form and congeal into clots.
  • atria executives sounded nearly that happy, too, both with the book and with their authors.
  • atria are for receiving blood ventricles are for pumping blood to the lungs and body.
British Dictionary definitions for atria


/ˈeɪtrɪəm; ˈɑː-/
noun (pl) 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
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
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Word Origin and History for atria

classical plural of atrium.



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.

Online Etymology Dictionary, © 2010 Douglas Harper
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atria in Medicine

atrium a·tri·um (ā'trē-əm)
n. pl. a·tri·ums or a·tri·a (ā'trē-ə)

  1. A chamber or cavity to which several chambers or passageways are connected.

  2. Either the right or the left upper chamber of the heart that receives blood from the veins and forces it into a ventricle.

  3. That part of the tympanic cavity that lies below the eardrum.

  4. 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.
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atria in Science
Plural atria or 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 © 2002. Published by Houghton Mifflin. All rights reserved.
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atria in Culture
atria [(ay-tree-uh)]

sing. atrium (ay-tree-uhm)

The two upper chambers in the heart, which receive blood from the veins and push it into the ventricles. (See circulatory system.)

The American Heritage® New Dictionary of Cultural Literacy, Third Edition
Copyright © 2005 by Houghton Mifflin Company.
Published by Houghton Mifflin Company. All rights reserved.
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