- calcium, Ca, atomic number 20 - a white metallic element that burns with a brilliant light; the fifth most abundant element in the earth's crust; an important component of most plants and animals
--1 is a kind of metallic element, metal
--1 is a substance of
--1 has particulars: calcium ion, factor IVcalcium oxide, quicklime, lime, calx, calcined lime, fluxing lime, unslaked lime, burnt lime; limestone; gypsum; fluorite, fluorspar, fluor - California, Golden State, CA, Calif. - a state in the western United States on the Pacific; the 3rd largest state; known for earthquakes
--2 is a kind of American state
--2 is a part of
--2 has parts: --2 has particulars: Colorado DesertUnited States, United States of America, America, US, U.S., USA, U.S.A.