1.NounThe simplest alkali metal, the lightest solid element, and the third lightest chemical element (symbol Li) with an atomic number of 3 and atomic weight of 6.94. It is a soft, silvery metal.
"The importance of lithium-ion batteries makes lithium a potentially strategic natural resource."
2.NounA single atom of this element.
3.NounLithium carbonate or other preparations of lithium metal used as a mood stabiliser to treat manic depression and bipolar disorders.
"It seems like his moods are better since he started taking lithium."