English Reference
noun

observer

n.
US /əbˈzɝvɝ/ UK /ɒbzˈɜːvɐ/ ob·serv·er UK spelling observers

  1. 01 B2 Upper Intermediate

    a person who watches or notices something carefully.

    an individual who monitors or takes notice of events, often to gain information or understanding.

    Simple

    A casual observer might not notice the small changes in the painting.

    In context

    To a trained observer, the subtle shifts in the bird's behaviour indicated that a predator was likely nearby in the tall grass.

  2. 02 B2 Upper Intermediate Formal

    a person sent to a meeting or election to watch but not take part.

    a representative delegated to attend a function or monitor a process to ensure fairness or gather data without active participation.

    Simple

    International observers were sent to make sure the election was fair.

    In context

    The organization sent several observers to the climate summit to report back on the progress of the negotiations without joining the voting process.

  3. 03 C1 Advanced Technical Military

    a soldier or crew member who watches for enemy positions.

    a person, such as a sentry or aircraft crew member, tasked with spotting enemy movements or identifying targets.

    Simple

    The observer used binoculars to scan the horizon for enemy ships.

    In context

    The forward observer relayed the exact coordinates of the artillery fire to the command centre via a secure radio link.

  4. 04 C2 Proficiency Formal Religion

    someone who follows a law, custom, or religious tradition.

    one who adheres to or complies with laws, guidelines, or religious requirements.

    Simple

    He was a strict observer of the Sabbath and never worked on Saturdays.

    In context

    As a lifelong observer of traditional customs, she insisted that the ceremony be performed exactly as it had been for generations.

    adherentfollower

Usage observer from knowing

This prevents an observer from knowing that you are communicating with us at all, let alone what is being said.

The Guardian· 13 Aug 2026

From observe + -er.

Etymology adapted from Wiktionary, available under CC BY-SA 4.0.

This entry
Level B2 · Upper Intermediate
Frequency Frequent
Updated