first lieutenant
noun /ˌfɜːst lefˈtenənt/
  /ˌfɜːrst luːˈtenənt/
 - an officer in the navy with responsibility for managing a ship, etc. under the guidance of the captain 舰务官 
- an officer in the US army and air force just below the rank of a captain(美国陆军和空军的)中尉 
- (informal) a person who is the next most important to somebody第二把手