secret service

government department dealing with espionage and counter-espionage 特务机关.

second in command, second lieutenant, second sight, second-best, second-degree, second-guess, second-hand, second-rate, second-string, secondarily, secondary, seconder, secondhand, secondly, secondment, secrecy, secrecy (title), secret, secret agent (also agent), secret police, secretarial, secretariat, secretary, Secretary of State, Secretary-General, secrete, secretion, secretive, secretively, secretiveness, secretly, sect, sectarian, sectarianism, section, sectional, sectionalism, sector, secular, secularism,