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[soh-dee-uh m] /ˈsoʊ di əm/
Chemistry. a soft, silver-white, metallic element that oxidizes rapidly in moist air, occurring in nature only in the combined state, and used in the synthesis of sodium peroxide, sodium cyanide, and tetraethyllead: a necessary element in the body for the maintenance of normal fluid balance and other physiological functions. Symbol: Na; atomic weight: 22.9898; atomic number: 11; specific gravity: 0.97 at 20°C.
Medicine/Medical, Pharmacology. any salt of sodium, as sodium chloride or sodium bicarbonate, present in or added to foods or beverages as a seasoning or preservative and used in many pharmaceutical products as an antacid, anticoagulant, or other agent.
Origin of sodium
From New Latin, dating back to 1800-10; See origin at soda, -ium Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2018.
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Examples from the Web for sodium
Contemporary Examples
Historical Examples
  • Oxygen will combine with iron or lead or sodium, but cannot be made to combine with fluorine.

    The Machinery of the Universe Amos Emerson Dolbear
  • You cannot do this experiment, however, as the sodium does its work so violently that it is dangerous.

    Common Science Carleton W. Washburne
  • For the saponification we employ a solution of sodium ethylate in the cold.

  • So it was a conversion of sodium chloride into sodium nitrate.

    Priestley in America Edgar F. Smith
  • It is a gray metal, considerably heavier and harder than sodium.

British Dictionary definitions for sodium


  1. a very reactive soft silvery-white element of the alkali metal group occurring principally in common salt, Chile saltpetre, and cryolite. Sodium and potassium ions maintain the essential electrolytic balance in living cells. It is used in the production of chemicals, in metallurgy, and, alloyed with potassium, as a cooling medium in nuclear reactors. Symbol: Na; atomic no: 11; atomic wt: 22.989768; valency: 1; relative density: 0.971; melting pt: 97.81±0.03°C; boiling pt: 892.9°C
  2. (as modifier): sodium light
Word Origin
C19: New Latin, from soda + -ium
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 sodium

metallic alkaline element, 1807, coined by English chemist Humphry Davy from soda; so called because the element was isolated from caustic soda (sodium hydroxide). The chemical symbol Na is from natrium, alternative name for the element proposed by Berzelius from natron, a name of a type of soda.

Online Etymology Dictionary, © 2010 Douglas Harper
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sodium in Medicine

sodium so·di·um (sō'dē-əm)
Symbol Na
A soft, light, highly reactive metallic element that is naturally abundant, especially in common salt. Atomic number 11; atomic weight 22.99; melting point 97.7°C; boiling point 883°C; specific gravity 0.971; valence 1.

The American Heritage® Stedman's Medical Dictionary
Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.
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sodium in Science
Symbol Na
A soft, lightweight, silvery-white metallic element of the alkali group that reacts explosively with water. It is the most abundant alkali metal on Earth, occurring especially in common salt. Sodium is very malleable, and its compounds have many important uses in industry. Atomic number 11; atomic weight 22.99; melting point 97.8°C; boiling point 892°C; specific gravity 0.971; valence 1. See Periodic Table.
The American Heritage® Science Dictionary
Copyright © 2002. Published by Houghton Mifflin. All rights reserved.
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