[dahy-uh g-nohs, -nohz, dahy-uh g-nohs, -nohz]

verb (used with object), di·ag·nosed, di·ag·nos·ing.

to determine the identity of (a disease, illness, etc.) by a medical examination: The doctor diagnosed the illness as influenza.
to ascertain the cause or nature of (a disorder, malfunction, problem, etc.) from the symptoms: The mechanic diagnosed the trouble that caused the engine knock.
to classify or determine on the basis of scientific examination.

verb (used without object), di·ag·nosed, di·ag·nos·ing.

to make a diagnosis.

Origin of diagnose

First recorded in 1860–65; back formation from diagnosis
Related formsdi·ag·nos·a·ble, adjectiveun·der·di·ag·nose, verb (used with object), un·der·di·ag·nosed, un·der·di·ag·nos·ing.un·di·ag·nos·a·ble, adjectiveun·di·ag·nosed, adjectivewell-di·ag·nosed, adjective
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019

Examples from the Web for diagnose

Contemporary Examples of diagnose

Historical Examples of diagnose

  • I will also diagnose your case, and advise you free of charge.

  • "I can diagnose the case more bluntly if you wish," he retorted.

    Howards End

    E. M. Forster

  • It may be difficult to diagnose exactly the mental symptoms.


    Hugo Mnsterberg

  • “Macgilpin, just diagnose this case for me,” cried the doctor to his assistant.

    Crown and Anchor

    John Conroy Hutcheson

  • I tried to diagnose her symptoms, but they were too complicated and contradictory.

    The Seven Secrets

    William Le Queux

British Dictionary definitions for diagnose



to determine or distinguish by diagnosis
(tr) to examine (a person or thing), as for a disease
Derived Formsdiagnosable, adjective
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Word Origin and History for diagnose

1861, back-formation from diagnosis. Related: Diagnosed; diagnosing.

Online Etymology Dictionary, © 2010 Douglas Harper

diagnose in Medicine


[dīəg-nōs′, -nōz′]


To distinguish or identify a disease by diagnosis.
To identify a person as having a particular disease or condition by diagnosis.
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.