Surveillance is the careful watching of someone, especially by an organization such as the police or the army.
双语例句
例： He was arrested after being kept under constant surveillance.
在被持续监视一段时间之后，他被逮捕了。
例： Police swooped on the home after a two-week surveillance operation.
在两周的监视后，警方突击搜查了该住宅。