diagnostic

1 of 2

adjective

di·​ag·​nos·​tic ˌdī-ig-ˈnä-stik 

-əg-

variants or less commonly diagnostical

ˌdī-ig-ˈnä-sti-kəl 

-əg-

1

a

: of, relating to, or used in diagnosis

a diagnostic tool

b

: using the methods of or yielding a diagnosis

diagnostic tests

2

: serving to distinguish or identify

a diagnostic feature

diagnostically

ˌdī-ig-ˈnä-sti-k(ə-)lē 

-əg-

adverb

diagnostic

2 of 2

noun

1

: the art or practice of diagnosis

—often used in plural

2

: a distinguishing mark

diagnostician

ˌdī-ig-(ˌ)nä-ˈsti-shən 

-əg-

noun

Synonyms of diagnostic

Adjective

• characteristic
• distinctive
• distinguishing
• distinct
• typical

Noun

• characteristic
• feature
• quality
• trait
• attribute
• attribution
• criterion

Examples of diagnostic in a Sentence

Adjective

Ultrasound is now widely used as a diagnostic tool.

One important diagnostic feature of this condition is a mild rash.

Noun

the thesis that moral decline is the infallible diagnostic of a decadent society

Recent Examples on the Web

Adjective

This requirement applies to a veterinarian, a veterinary diagnostic laboratory, or a person having care, custody, or control of an animal. —Fousia Abdullahi, Fort Worth Star-Telegram, 24 Nov. 2025

In a healthy person without neurological complaints, a brain MRI serves as an essential diagnostic tool for evaluating brain health. —Sandra Rose Salathe, Flow Space, 21 Nov. 2025

Noun

Turn off cloud diagnostics to reduce the footprint of unsupported smart products. —Kurt Knutsson, FOXNews.com, 25 Nov. 2025

The analysts, who kept their hold rating, said the life sciences and diagnostics company delivered a solid quarter. —Jim Cramer, CNBC, 25 Nov. 2025

Word History

First Known Use

Adjective

1625, in the meaning defined at sense 1a

Noun

1625, in the meaning defined at sense 1

Rhymes for diagnostic

• acrostic
• agnostic
• encaustic
• prognostic
• caustic
• gnostic

Kids Definition

diagnostic

adjective

di·​ag·​nos·​tic

ˌdī-ig-ˈnäs-tik

: of, relating to, or used in diagnosis

a diagnostic test for heart disease

Medical Definition

diagnostic

1 of 2 adjective

di·​ag·​nos·​tic -ˈnäs-tik 

variants also diagnostical

-ti-kəl 

1

: of, relating to, or used in diagnosis

2

: using the methods of or yielding a diagnosis

a diagnostic service

diagnostic properties

diagnostically

-ti-k(ə-)lē 

adverb

diagnostic

2 of 2 noun

: the art or practice of diagnosis

—often used in plural