an act or instance of circulating, moving in a circle or circuit, or flowing.
the continuous movement of blood through the heart and blood vessels, which is maintained chiefly by the action of the heart, and by which nutrients, oxygen, and internal secretions are carried to and wastes are carried from the body tissues.
any similar circuit, passage, or flow, as of the sap in plants or air currents in a room.
the transmission or passage of anything from place to place or person to person: the circulation of a rumor; the circulation of money.
the distribution of copies of a periodical among readers.
the number of copies of each issue of a newspaper, magazine, etc., distributed.
coins, notes, bills, etc., in use as money; currency.
Library Science.
the lending of library books and other materials.
the number of books and materials that a library has lent.
the processes connected with providing for the use of library materials, including reserve operations, recall, and record-keeping.
Hydraulics. a quantity analogous to work and equal to the line integral of the component of fluid velocity about a closed contour.
in circulation, participating actively in social or business life: After a month in the hospital, he's back in circulation.

1400–50 for an earlier alchemical sense; 1645–55 for def 1; late Middle English circulacioun < Latin circulātiōn- (stem of circulātiō), equivalent to circulāt(us) (see circulate) + -iōn- -ion

circulable [sur-kyuh-luh-buhl] , adjective
intercirculation, noun
noncirculation, noun
precirculation, noun
recirculation, noun Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2014.
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World English Dictionary
circulation (ˌsɜːkjʊˈleɪʃən)
1.  the transport of oxygenated blood through the arteries to the capillaries, where it nourishes the tissues, and the return of oxygen-depleted blood through the veins to the heart, where the cycle is renewed
2.  the flow of sap through a plant
3.  any movement through a closed circuit
4.  the spreading or transmission of something to a wider group of people or area
5.  (of air and water) free movement within an area or volume
6.  a.  the distribution of newspapers, magazines, etc
 b.  the number of copies of an issue of such a publication that are distributed
7.  library science
 a.  a book loan, as from a library lending department
 b.  each loan transaction of a particular book
 c.  the total issue of library books over a specified period
8.  a rare term for circulating medium
9.  in circulation
 a.  (of currency) serving as a medium of exchange
 b.  (of people) active in a social or business context

Collins English Dictionary - Complete & Unabridged 10th Edition
2009 © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins
Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009
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Word Origin & History

1440, from L. circulationem, from circulare "to form a circle," from circulus "small ring" (see circle). Used of blood first by William Harvey, 1628.
Online Etymology Dictionary, © 2010 Douglas Harper
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American Heritage
Medical Dictionary

circulation cir·cu·la·tion (sûr'kyə-lā'shən)
Movement in a circle or circuit, especially the movement of blood through bodily vessels as a result of the heart's pumping action.

The American Heritage® Stedman's Medical Dictionary
Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.
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American Heritage
Science Dictionary
circulation   (sûr'kyə-lā'shən)  Pronunciation Key 
The flow of fluid, especially blood, through the tissues of an organism to allow for the transport and exchange of blood gases, nutrients, and waste products. In vertebrates, the circulation of blood to the tissues and back to the heart is caused by the pumping action of the heart. Oxygen-rich blood is carried away from the heart by the arteries, and oxygen-poor blood is returned to the heart by the veins. The circulation of lymph occurs in a separate system of vessels (the lymphatic system). Lymph is pumped back to the heart by the contraction of skeletal muscles.
The American Heritage® Science Dictionary
Copyright © 2002. Published by Houghton Mifflin. All rights reserved.
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American Heritage
Idioms & Phrases


see in circulation; out of circulation.

The American Heritage® Dictionary of Idioms by Christine Ammer.
Copyright © 1997. Published by Houghton Mifflin.
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Example sentences
What are the effects on atmospheric circulation as sulfates are added to the
  atmosphere in irregular distribution patterns.
Do check the air circulation vents for your building.
Because of the low air pressure, the body overcompensates and speeds up its
  blood circulation.
Among the home's defects was poor circulation as a result of bedrooms that
  functioned as hallways.
Image for circulation
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