n. Chem. a soft silver-white reactive metallic element, occurring naturally in soda, salt, etc., that is important in industry and is an essential element in living organisms.
Phrases and idioms:
sodium bicarbonate a white soluble powder used in the manufacture of fire extinguishers and effervescent drinks. sodium carbonate a white powder with many commercial applications including the manufacture of soap and glass. sodium chloride a colourless crystalline compound occurring naturally in sea water and halite; common salt. sodium hydroxide a deliquescent compound which is strongly alkaline and used in the manufacture of salt and pepper: also called caustic soda. sodium nitrate a white powdery compound used mainly in the manufacture of fertilizers. sodium-vapour lamp (or sodium lamp) a lamp using an electrical discharge in sodium vapour and giving a yellow light.
Etymology: SODA + -IUM