detective

 
Pronunciation: /dɪˈtɛktɪv/

noun

  • a person, especially a police officer, whose occupation is to investigate and solve crimes: detectives are anxious to interview anyone who saw the car
  • [as modifier] denoting a rank of police officer with investigative duties: a detective inspector
  • [as modifier] concerning crime and its investigation: detective work

Origin:

mid 19th century: from detect. The noun was originally short for detective policeman, from an adjectival use of the word in the sense 'serving to detect'