The chemical element (Symbol Ca), with an atomic number 20. It is a soft, silvery-white alkaline earth metal which occurs naturally as carbonate in limestone and as silicate in many rocks.

plural of calcium

(inorganic chemistry) The yellow calcium salt of chromic acid, CaCrO₄

(pharmacology) The salt form of the protease inhibitor drug fosamprenavir used in the treatment of HIV infected patients.

(inorganic chemistry) The calcium salt of phosphoric acid, Ca₃(PO₄)₂, or of several related acids; it is the main mineral of bone

Alternative spelling of calcium sulfate

(inorganic chemistry) The calcium salt of sulfuric acid, CaSO₄, the hydrates of which are known as gypsum or plaster of Paris, and the anhydrous mineral form being anhydrite.

(inorganic chemistry) A white powderous substance, CaO, normally made by heating calcium carbonate.

(inorganic chemistry) A soft, white powder, Ca(OH)₂, obtained by the action of water on calcium oxide; slaked lime.

(physics) A radioactive isotope of calcium, ⁴⁵₂₀Ca, having twenty protons and twenty-five neutrons, and a half-life of 162.6 days; it is used as a tracer in studying calcium metabolism. As it decays it undergoes transformation (nuclear transmutation) via electron emission, also called negative beta decay (β−-decay), into scandium.