English Reference
verb

diagnose

v.
US /ˌdaɪəɡˈnoʊs/ UK /dˌaɪəɡnˈəʊz/ di·ag·nose UK spelling diagnosed, diagnosing

  1. 01 B2 Upper Intermediate Medicine

    to identify a disease or illness by looking at a person's symptoms.

    to identify the nature of an illness or other medical condition by examination of the symptoms. Transitive, taking the condition or the patient as the direct object.

    Simple

    The doctor diagnosed her with a mild allergy after she developed a rash.

    In context

    Specialists spent weeks running tests before they could accurately diagnose the rare genetic condition affecting the patient's nervous system.

    Usage

    Commonly used in the passive voice: 'He was diagnosed with...'

    Pitfall
    The doctor diagnosed him for the flu. The doctor diagnosed him with the flu.

    Use the preposition 'with' to connect the patient to the specific illness.

  2. 02 C1 Advanced Technical

    to find the exact cause of a problem with a machine, a system, or a situation.

    to determine the cause of a mechanical failure, technical fault, or systemic problem through systematic analysis.

    Simple

    The mechanic used a computer to diagnose the fault in the car's engine.

    In context

    The consultant was hired to diagnose the underlying issues that were causing the company's sudden drop in productivity.

    Usage

    Often takes an abstract noun like 'problem', 'fault', or 'issue' as a direct object.

    analyzetroubleshootpinpoint

Usage diagnosed with autism

Shortly after the COVID-19 lockdown began, Ashleigh Bell Pedersen was diagnosed with an aggressive form of breast cancer.

NPR· 11 Aug 2026

Paul Eatwell, 65, was diagnosed after a routine blood test.

BBC News· 11 Aug 2026

Back-formation from diagnosis. Compare also sclerose (verb).

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

This entry
Level C1 · Advanced
Frequency Frequent
Updated