sodium

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun A soft, light, extremely malleable silver-white element that is an alkali metal, reacts violently with water, is naturally abundant in combined forms, especially in common salt, and is used in the production of a wide variety of industrially important compounds. Sodium ions are essential to numerous biological processes in animals. Atomic number 11; atomic weight 22.9898; melting point 97.80°C; boiling point 883°C; specific gravity 0.971 (20°C); valence 1. cross-reference: Periodic Table.

from The Century Dictionary.

• noun Chemical symbol, Na (natrium); atomic weight, 23. The metallic base of the alkali soda. See soda and metallurgy

from the GNU version of the Collaborative International Dictionary of English.

• noun (Chem.) A common metallic element of the alkali group, in nature always occuring combined, as in common salt, in albite, etc. It is isolated as a soft, waxy, white, unstable metal, so highly reactive that it combines violently with water, and to be preserved must be kept under petroleum or some similar liquid. Sodium is used combined in many salts, in the free state as a reducer, and as a means of obtaining other metals (as magnesium and aluminium) is an important commercial product. Symbol Na (Natrium). Atomic weight 22.990. Specific gravity 0.97.
• noun an alloy of sodium and mercury, usually produced as a gray metallic crystalline substance, which is used as a reducing agent, and otherwise.
• noun a white crystalline substance, Na2CO3.10H2O, having a cooling alkaline taste, found in the ashes of many plants, and produced artifically in large quantities from common salt. It is used in making soap, glass, paper, etc., and as alkaline agent in many chemical industries. Called also sal soda, washing soda, or soda. Cf. Sodium bicarbonate, and Trona.
• noun common, or table, salt, NaCl.
• noun a white opaque brittle solid, NaOH, having a fibrous structure, produced by the action of quicklime, or of calcium hydrate (milk of lime), on sodium carbonate. It is a strong alkali, and is used in the manufacture of soap, in making wood pulp for paper, etc. Called also sodium hydrate, and caustic soda. By extension, a solution of sodium hydroxide.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun A soft, waxy, silvery reactive metal that is never found unbound in nature, and a chemical element (symbol Na) with an atomic number of 11 and atomic weight of 22.98977.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun a silvery soft waxy metallic element of the alkali metal group; occurs abundantly in natural compounds (especially in salt water); burns with a yellow flame and reacts violently in water; occurs in sea water and in the mineral halite (rock salt)