1.NounThe process of, or an instance of, identification of the nature and cause of a medical condition or illness.
"Diagnosis is a challenging art informed by wide-ranging science.; He was given the wrong treatment due to an erroneous diagnosis.; Her diagnoses include type 2 diabetes mellitus, primary hypertension, diabetic retinopathy, and generalized anxiety disorder."
2.NounThe process of, or an instance of, identification of the nature and cause of something (of any nature).
"Diagnosis is part of being an automotive mechanic.; Her diagnosis of the current economic situation is that central banks are overcorrecting."
3.NounA written description of a species or other taxon serving to distinguish that species from all others; especially a description written and published in Latin.