[puh-tas-ee-uh m]
noun Chemistry.
  1. a silvery-white metallic element that oxidizes rapidly in the air and whose compounds are used as fertilizer and in special hard glasses. Symbol: K; atomic weight: 39.102; atomic number: 19; specific gravity: 0.86 at 20°C.

Origin of potassium

From New Latin, dating back to 1800–10; see origin at potassa, -ium
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018

Examples from the Web for potassium

Contemporary Examples of potassium

Historical Examples of potassium

  • The most important are carbonate of soda, potash, and cyanide of potassium.

  • Potassium nitrate, 75 parts; charcoal, 15 parts; sulphur, 10 parts.

  • He did so, and gave me daily a teaspoonful of bromide of potassium.


    Charles Godfrey Leland

  • This is a sign that the bath is deficient in potassium cyanide.

    On Laboratory Arts

    Richard Threlfall

  • They are then dipped for a moment in a boiling solution of potassium cyanide.

    On Laboratory Arts

    Richard Threlfall

British Dictionary definitions for potassium


  1. a light silvery element of the alkali metal group that is highly reactive and rapidly oxidizes in air; occurs principally in carnallite and sylvite. It is used when alloyed with sodium as a cooling medium in nuclear reactors and its compounds are widely used, esp in fertilizers. Symbol: K; atomic no: 19; atomic wt: 39.0983; valency: 1; relative density: 0.862; melting pt: 63.71°C; boiling pt: 759°C
Derived Formspotassic, adjective

Word Origin for potassium

C19: New Latin potassa potash
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

Word Origin and History for potassium

metallic element, 1807, coined by English chemist Sir Humphrey Davy (1778-1829) from Modern Latin potassa, Latinized form of potash (q.v.). Davy first isolated it from potash. Symbol K is from Latin kalium "potash," from Arabic al-qaliy "the ashes, burnt ashes" (see alkali).

Online Etymology Dictionary, © 2010 Douglas Harper

potassium in Medicine


n. Symbol K
  1. A soft, highly or explosively reactive metallic element that occurs in nature only in compounds and is found in or converted to a wide variety of salts used especially in fertilizers and soaps. Its radioisotopes are used in various diagnostic studies, including myocardial scans, detection and localization of tumors, determination of intracellular fluid space, and determination of renal blood flow. Atomic number 19.kalium
Related formspo•tassic adj.
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.

potassium in Science


  1. A soft, highly reactive, silvery-white metallic element of the alkali group occurring in nature only in compounds. It is essential for the growth of plants and is used especially in fertilizers and soaps. Atomic number 19; atomic weight 39.098; melting point 63.65°C; boiling point 774°C; specific gravity 0.862; valence 1. See Periodic Table.
The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.