<p><strong>Noun:</strong></p><ul><li>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.</li><li>A necessary element in the body for the maintenance of normal fluid balance and other physiological functions.</li><li>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.</li></ul>