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

Ringel sees Nome as providing insight after a diagnostic test. — Brad Quick, CNBC, 18 Aug. 2026

Therefore, turning to emotions as diagnostic information is a way to start improving the systems that shape them. — Naira Velumyan, Forbes.com, 17 Aug. 2026

Noun

The Broadband Forum says that could include everything from diagnostics and customer support tools to automations and energy management services. — Paul Lamkin, Forbes.com, 18 Aug. 2026

Testing includes blood work, genetic screening, ultrasounds, a DEXA body-composition scan, cardiovascular assessments, and numerous other diagnostics, with every result explained immediately and paired with practical recommendations. — Ken Gawrych, Robb Report, 16 Aug. 2026

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