diagnostic

American  

[dahy-uhg-nos-tik] / ˌdaɪ əgˈnɒs tɪk /

adjective

1. of, relating to, or used in diagnosis.

2. serving to identify or characterize; being a precise indication.

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noun

1. diagnosis.

2. a symptom or characteristic of value in diagnosis.

3. Medicine/Medical. a device or substance used for the analysis or detection of diseases or other medical conditions.

4. Computers.

   1. a message output by a computer diagnosing an error in a computer program, computer system, or component device.

   2. a program or subroutine that produces such messages.

diagnostic British  

/ ˌdaɪəɡˈnɒstɪk /

adjective

1. of, relating to, or of value in diagnosis

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noun

1. med any symptom that provides evidence for making a specific diagnosis

2. a diagnosis

Other Word Forms

• diagnostically adverb
• postdiagnostic adjective
• prediagnostic adjective

Etymology

Origin of diagnostic

1615–25; < Greek diagnōstikós, equivalent to diagnōst ( ós ) distinguished (akin to diágnōsis; see diagnosis) + -ikos -ic

Explanation

Anything diagnostic has to do with disease, especially figuring out which one a patient has. If your doctor wants to run diagnostic tests, then she isn't exactly sure what's wrong with you — so the tests will help diagnose you (figure out what's wrong). The TV show House is all about diagnostic tests: it features illnesses that are unusual and hard to determine. But anything diagnostic is trying to figure out what's wrong. A writing test could be called diagnostic if it's trying to determine how good or bad your writing skills are.

Example Sentences

Even so, most teens are not learning core skills — more than 50% failed a diagnostic test from the National Financial Educators Council, and the average score among 15- to 18-year-olds was just 64%.

From MarketWatch • Apr. 21, 2026

Profit fell in the recent period, as sales of certain diagnostic tests were stymied by the mild respiratory season.

From The Wall Street Journal • Apr. 16, 2026

Baffert said the filly appeared OK but would undergo diagnostic tests to be sure.

From Los Angeles Times • Apr. 4, 2026

"Wrinkly can be mean lots of things, so there's a lack of diagnostic language."

From Science Daily • Apr. 3, 2026

But storing tissues from diagnostic procedures like, say, mole biopsies, and using them in future research doesn’t require such consent.

From "The Immortal Life of Henrietta Lacks" by Rebecca Skloot