calcium

[kal-see-uhm]
noun Chemistry, Biology.
a silver-white divalent metal, occurring combined in limestone, chalk, gypsum, etc., occurring also in vertebrates and other animals, as a component of bone, skeletal mass, shell, etc., and as a necessary element in nerve conduction, heartbeat, muscle contraction, and many other physiological functions. Symbol: Ca; atomic weight: 40.08; atomic number: 20; specific gravity: 1.55 at 20°C.

Origin:
1800–10; calc- + -ium

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World English Dictionary
calcium (ˈkælsɪəm)
 
n
a malleable silvery-white metallic element of the alkaline earth group; the fifth most abundant element in the earth's crust (3.6 per cent), occurring esp as forms of calcium carbonate. It is an essential constituent of bones and teeth and is used as a deoxidizer in steel. Symbol: Ca; atomic no: 20; atomic wt: 40.078; valency: 2; relative density: 1.55; melting pt: 842±2°C; boiling pt: 1494°C
 
[C19: from New Latin, from Latin calx lime]

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Etymonline
Word Origin & History

calcium
coined 1808 by Sir Humphry Davy from L. calx (gen. calcis) "limestone" (see chalk).
Online Etymology Dictionary, © 2010 Douglas Harper
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American Heritage
Medical Dictionary

calcium cal·ci·um (kāl'sē-əm)
n.
Symbol Ca
A soft metallic element that is a basic component of animals and plants and constitutes [approx] 3 percent of Earth's crust. It occurs naturally in limestone, gypsum, and fluorite. Atomic number 20; atomic weight 40.08; melting point 842°C; boiling point 1,484°C; specific gravity 1.55; valence 2.

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Science Dictionary
calcium   (kāl'sē-əm)  Pronunciation Key 
Symbol Ca
A silvery-white, moderately hard metallic element of the alkaline-earth group that occurs in limestone and gypsum. It is a basic component of leaves, bones, teeth, and shells, and is essential for the normal growth and development of most animals and plants. Calcium is used to make plaster, cement, and alloys. Atomic number 20; atomic weight 40.08; melting point 842 to 848°C; boiling point 1,487°C; specific gravity 1.55; valence 2. See Periodic Table.
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Copyright © 2002. Published by Houghton Mifflin. All rights reserved.
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Example sentences
Ionized calcium is calcium that is freely flowing in your blood and not
  attached to proteins.
The mineral in question is calcium carbonate, the defining ingredient of
  limestone.
Calcite and aragonite are the two crystal forms of calcium carbonate, a
  property of minerals geologists call dimorphism.
Plant scientists have long suspected calcium as a key player in controlling the
  action of the stomata.
Images for calcium
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