diagnostic UK /daɪ.əɡˈnɒs.tɪk/US /ˌdaɪ.əɡˈnɑ.stɪk/adjective 5noun 3forms 3 adjective5 •Of, or relating to diagnosis. •Intended to assess a student's preexisting knowledge on the material being taught. •Characteristic of a particular disease. •Serving to indicate or specify a particular item or thing within a group of similar things. •Characteristic of a particular taxon or clade. noun3 •Any technique used in medical diagnosis. •Any tool or technique used to find the root of a problem. •That by which anything is known; a symptom. formsdiagnostics · more diagnostic · most diagnostic