surveillance

surveillance — noun

1. the activity of closely watching people, buildings, or areas to prevent or solve

1.nounB2
Definition

the activity of closely watching people, buildings, or areas to prevent or solve crimes and to collect information for security purposes

Example

Surveillance of the warehouse showed workers leaving goods by the back door at night.

The bank manager was kept under police surveillance for three days after the robbery.

collocation: under surveillance

Common collocations
  • under surveillance
  • keep under surveillance
  • surveillance camera
  • surveillance footage
  • surveillance system
  • electronic surveillance
  • police surveillance
  • close surveillance
Synonyms
  • monitoring

    broader term; can refer to routine or technical observation (e.g., health monitoring), not only for crime prevention

  • observation

    more neutral and general; used in science, medicine, and everyday contexts, not necessarily secretive

  • watch

    informal and shorter; often used in 'keep watch' or 'under watch,' less technical than surveillance

Grammar Patterns

under + surveillance

surveillance + noun (as modifier)

Usage Note

Uncountable noun — do not say 'a surveillance' or 'surveillances.' The idiomatic pattern is 'keep someone/something under surveillance.' Also commonly used as a modifier before nouns ('surveillance camera,' 'surveillance footage').

Common Mistakes

The police kept surveillance on the suspect.
The police kept the suspect under surveillance.
The correct idiomatic pattern is 'keep [someone/something] under surveillance,' not 'keep surveillance on.'

Word family

  • surveil
    verbC1

Synonym discussion

Sense: noun/1

All four words involve paying attention to someone or something, but they differ in context and connotation. Surveillance is the most specific — it implies secret or official watching by authorities for security or law-enforcement purposes, often using technology. Monitoring is broader and more neutral; you can monitor your blood pressure, website traffic, or a child's screen time. Observation is the most general and can be scientific, medical, or casual. Watch is informal and usually implies active attention ('keep watch,' 'under watch'). Oversight focuses on supervision and ensuring rules are followed, not on secret monitoring. For example: 'The police kept the building under surveillance,' but 'The teacher monitored the students during the exam' and 'A manager provides oversight of daily operations.'

monitoringobservation ↗watch ↗oversight ↗

Common collocations

Nouns

Adverbs

Phrases

  • under surveillance
  • electronic surveillance
  • police surveillance
  • video surveillance
  • put under surveillance

Prepositions

Etymology

LatinFrenchEnglish

Surveillance entered English in the early 1800s from French 'surveillance,' meaning 'a watching over.' The French word comes from 'sur-' (over) and 'veiller' (to watch), which traces back to Latin 'vigilare' (to stay awake, keep watch). Its earliest English uses were in military and police contexts, and it has since expanded to cover all forms of official monitoring.