资料来源 : pyDict

第十亿的,十亿分之一的第十亿,十亿分之一

资料来源 : WordNet®

billionth
     adj : the ordinal number of one billion in counting order
     n 1: position 1,000,000,000 in a countable series of things
     2: one part in a billion [syn: {one-billionth}]