plutonium
/pluːˈtəʊnɪəm/noun
mass noun
- the chemical element of atomic number 94, a dense silvery radioactive metal of the actinide series, used as a fuel in nuclear reactors and as an explosive in nuclear fission weapons. Plutonium only occurs in trace amounts in nature but is manufactured in nuclear reactors from uranium-238. (Symbol:Pu)（化学元素）钚（符号： Pu）。
词源
late 18th cent.: from Greek 'Pluto'， on the pattern of neptunium, being the next planet beyond Neptune.