English Reference
noun · verb

lesion

n. · v.
US /ˈɫiʒən/ UK /lˈiːʒən/ le·sion UK spelling lesioned, lesions

  1. 01 C1 Advanced Technical Medicine

    n.an area of the body, such as the skin or an organ, that has been damaged by a disease or an injury.

    n.a localized area of diseased or damaged tissue, such as a wound, ulcer, or tumor. Often used as a general term in clinical diagnosis before a specific cause is identified.

    Simple

    The doctor examined the small red lesion on the patient's arm to see if it was an infection.

    In context

    The MRI scan revealed a small lesion in the left hemisphere of the brain, which explained the patient's sudden loss of motor coordination.

    Usage

    Commonly used with adjectives like 'skin', 'brain', 'benign', or 'malignant'.

  2. 02 C2 Proficiency FormalTechnical Law

    n.a situation where a contract is so unfair that one person loses a lot of money.

    n.the injury or harm suffered by a party to a contract who does not receive the equivalent of what they give, potentially allowing the contract to be cancelled.

    Simple

    The lawyer argued that the sale of the house was a case of lesion because the price was far too low.

    In context

    Under certain civil law jurisdictions, a contract may be rescinded on the grounds of lesion if the price paid is less than half the fair market value.

    Teacher's tip

    This sense is rare outside of specific legal systems like those in France, Quebec, or Louisiana.

    inequityimbalance
  3. 03 C2 Proficiency Technical Science

    v.to damage a specific part of a body, usually during a scientific experiment.

    v.to intentionally create a lesion in an organ or tissue, typically for the purpose of scientific research or medical treatment.

    Simple

    Scientists lesioned a small part of the bird's brain to study how it learned songs.

    In context

    The researchers lesioned specific neural pathways in the laboratory mice to observe the resulting changes in social behavior.

    Usage

    This verb is transitive and almost exclusively used in academic or laboratory contexts.

What began as an effort to explain black lesions on a common catfish may help us better understand cancer, evolution and infectious disease in all animals, including ourselves.

Phys.org· 19 Aug 2026

Using microscopes, 3D scans and tissue-loss measurements, we documented even the smallest lesions.

ScienceDaily· 8 Jun 2026

From Middle English lesioun, from Old French lesion, from Latin laesiō (“injury”), itself from laesus, perfect passive participle of laedō (“I injure, hurt”).

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

This entry
Origin Latin laesiō
Level C1 · Advanced
Frequency Occasional
Updated