sur·veil·lance 
/sɚˈveɪləns/ noun
/sɚˈveɪləns/ noun [noncount] : the act of carefully watching someone or something especially in order to prevent or detect a crime
▪ government surveillance of suspected terrorists ▪ The bank robbery was recorded by surveillance video cameras. ▪ electronic surveillance [=the act of using electronic devices to watch people or things] ▪ The police kept her under surveillance. [=watched her closely]
▪ government surveillance of suspected terrorists ▪ The bank robbery was recorded by surveillance video cameras. ▪ electronic surveillance [=the act of using electronic devices to watch people or things] ▪ The police kept her under surveillance. [=watched her closely]
