lith ‧ i ‧ um /ˈlɪθiəm/ BrE AmE noun [uncountable]
[ Date: 1800-1900 ; Language: Greek ; Origin: lithos 'stone' ]
a soft silver-white metal that is the lightest known metal, is used in BATTERIES , and is often combined with other metals. It is a chemical ↑ element : symbol Li