DIAGNOSTIC, adjective [Gr., to know.] Distinguishing; characteristic; indicating the nature of a disease. DIAGNOSTIC, noun The sign or symptom by which a disease is known or distinguished from others. Diagnostics are of two kinds; the adjunct, or such as are common to several diseases; and the pathognomonic, which always attend the disease, and distinguish it from all others.
Source: Webster's 1828 American Dictionary ↗ · public-domain · returned verbatim, no AI