define sodium wikipedia
Sodium is an essential element for all animals and some plants. Sodium ions are the major cation in the extracellular fluid (ECF) and as such are the major contributor to the ECF osmotic pressure, and thus ECF compartment volume.any sodium compounds are useful, such as sodium hydroxide (lye) for soap-making and sodium chloride for use as a de-icing agent and a nutrient (edible salt).