surveillance
n. uncountablen. the careful watching of a person or place, especially by the police or army, to stop a crime or gather information.
n. the close observation of a person, group, or area, particularly for the purpose of security or criminal investigation.
The police kept the building under surveillance for several weeks.
Modern cities often use a network of cameras for constant surveillance to help reduce crime in public spaces.
The intelligence agency maintained strict surveillance on the suspect's digital communications, hoping to intercept evidence of the planned security breach before it could be executed.
Unadapted borrowing from French surveillance (“a watching over, overseeing, supervision”), from surveiller (“to watch, oversee”), from sur- (“over”) + veiller (“to watch”), from Middle French, from Old French veillier (“to stay awake”), from Latin vigilāre (“to be watchful”). More at vigilant.
Commonly used in the phrase 'under surveillance'. Often paired with the verbs 'conduct', 'maintain', or 'perform'.
The police made a surveillanceThe police conducted surveillanceSurveillance is uncountable and does not take the indefinite article 'a'; it also collocates with 'conduct' or 'perform' rather than 'make'.