O
old-age pension                                                                         n.      养老保险制度
oligarchy  [ ]                                    n.  寡头政治, 寡头政治的执政团
oligopoly   [ ]                                      n.     求过于供的市场情况
on-the-job training                                       n.    岗位培训    
opportunity cost                                         n.    机会成本
optimize (maximize / minimize)                     v.  优化 / 最大化/ 最小化
overheating                                              n.  过热