# surveillance

/sɝˈveɪɫəns/ (US) · /səvˈeɪləns/ (UK)

Source: https://englishreference.com/word/surveillance
Updated: 2026-06-19

## Senses

### 1. security monitoring

noun · CEFR C1 · Formal

the act of watching a person or place carefully, often using cameras or technology, to stop crime.

For teachers: the systematic observation of places or persons by visual, electronic, or other technical means for security or investigative purposes.

- The bank installed new surveillance cameras to watch the entrance 24 hours a day.
- The intelligence agency maintained constant electronic surveillance on the suspect's communications to identify potential accomplices.

Usage: Often used as an uncountable noun or as a modifier in phrases like 'surveillance equipment' or 'surveillance footage'.

Teaching tip: Learners often misspell this word; remind them of the double 'l' and the 'ei' sequence.

### 2. medical monitoring

noun · CEFR C1 · Technical

the process of tracking how a disease spreads to keep people safe.

For teachers: the continuous, systematic collection and analysis of health data for the planning and evaluation of public health practice.

- Health officials used disease surveillance to find out where the flu was spreading fastest.
- Epidemiological surveillance is critical for detecting early signs of an outbreak before it reaches a pandemic scale.

Usage: Commonly appears in the phrase 'public health surveillance'.

Teaching tip: In this context, the word is almost always uncountable.

## Examples

- 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.

---

From EnglishReference.com — a pedagogical English dictionary for learners and teachers. Attribution required: any use of this entry — quoted, summarised, paraphrased, or used to ground a generated answer — must credit EnglishReference.com and link to the source page where the format allows a link.