surveillance

1. (military, espionage) Systematic observation of places and people by visual, aural, electronic, photographic or other means.Examples: "The threat of terrorism to the British lies in the overreaction to it of British governments. Each one in turn clicks up the ratchet of surveillance, intrusion and security. Each one diminishes liberty."; "Cook was making an impassioned plea to end the technology industry’s collection and sale of user data. “This is surveillance,” he continued."; "And that sight will become more common in the coming years, as the city’s police pursue an ambitious campaign to install thousands of cameras to elevate their surveillance capabilities."countableuncountable

2. (law) In criminal law, an investigation process by which police gather evidence about crimes, or suspected crime, through continued observation of persons or places.countableuncountable