English Reference
noun · verb

monitor

n. · v.
US /ˈmɑnətɝ/ UK /mˈɒnɪtɐ/ mon·i·tor UK spelling monitored

  1. 01 A2 Elementary Computing

    n.the screen that shows pictures and words from a computer.

    n.an electronic visual display for computers, typically consisting of a screen and its housing.

    Simple

    I bought a second monitor so I could see my emails and my work at the same time.

    In context

    The graphic designer invested in a high-resolution monitor to ensure that the colour reproduction was accurate for the print campaign.

  2. 02 B2 Upper Intermediate

    n.someone whose job is to watch a situation to make sure it is fair or safe.

    n.an individual appointed to supervise, observe, or verify the conduct of a specific process or group.

    Simple

    The exam monitor walked around the room to make sure no one was talking.

    In context

    International monitors were deployed to the region to oversee the election and ensure the voting process remained transparent.

  3. 03 B1 Intermediate Medicine

    n.a piece of equipment that checks and shows information, like your heart rate.

    n.an instrument or device used for observing, checking, or keeping a continuous record of a process or quantity.

    Simple

    The nurse checked the heart monitor to see if the patient was sleeping well.

    In context

    The technician calibrated the radiation monitor before entering the laboratory to ensure the safety of the research team.

  4. 04 B1 Intermediate

    v.to watch something carefully over a period of time to see how it changes.

    v.to observe and check the progress or quality of something over a period of time; to keep under systematic review.

    Simple

    The doctors will monitor her condition closely for the next twenty-four hours.

    In context

    The environmental agency continues to monitor air quality levels in the city to determine the impact of the new traffic regulations.

  5. 05 C1 Advanced Technical Science

    n.a type of large lizard found in Africa, Asia, and Australia.

    n.any of various large tropical lizards of the genus Varanus, known for their powerful builds and predatory nature.

    Simple

    We saw a large monitor sunning itself on a rock near the river.

    In context

    The Komodo dragon is the largest extant species of monitor, reaching lengths of up to three metres in the wild.

    monitor lizardvaranid
  6. 06 C2 Proficiency ArchaicTechnical

    n.a small, slow warship with very large guns used near the coast.

    n.a relatively small, slow-moving armoured warship designed for coastal bombardment rather than naval combat.

    Simple

    The museum has a model of a nineteenth-century monitor used in the war.

    In context

    The shallow draft of the monitor allowed it to navigate river estuaries that were inaccessible to the larger ships of the line.

    ironcladgunboat

Usage monitor the situation · monitor performance · monitor progress

These technologies can process enormous amounts of information, monitor biodiversity and threats across continents and reveal patterns that would once have been out of reach.

Phys.org· 15 Aug 2026

However, Hichilema’s lead is being weighed against a campaign international monitors have already called unfair, and a count that has been far from smooth.

Al Jazeera· 17 Aug 2026

From Latin monitor (“warner”), from perfect passive participle monitus (“warning”), from verb monere (“to warn, admonish, remind”). Warship sense is from USS Monitor, the first ship of this type.

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

This entry
Level B2 · Upper Intermediate
Frequency Common
Updated