Pronunciation: (lith'ē-um), [key]
1. Chem.a soft, silver-white metallic element, the lightest of all metals, occurring combined in certain minerals. Symbol: Li; at. wt.: 6.939; at. no.: 3; sp. gr.: 0.53 at 20°C.
2. Pharm.the substance in its carbonate or citrate form used in the treatment or prophylaxis of bipolar disorder or mania.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.