first aid急救firstadj.第一的；最初的adv.首先；第一n.最初；(序数词)第一first-order necessary condition一阶必要条件First Assignable Instructor Pilot由毕业学员直接升任教官的飞行员first-order phase-locked loop一阶锁相环First Bus Customer Service Centre新巴顾客服务中心First-Order Hyperbolic EquationFIRST X'MAS IN FOREIGN COUNTRY.First filial generation of hybrid杂一代first fundamental form of surface曲面的第一基本形式first-landfall tropical cyclone初旋First class or economy class?