Source : Webster's Revised Unabridged Dictionary (1913)

Diagnostics \Di`ag*nos"tics\, n.
   That part of medicine which has to do with ascertaining the
   nature of diseases by means of their symptoms or signs.

         His rare skill in diagnostics.           --Macaulay.

Source : WordNet®

diagnostics
     n : the branch of medical science dealing with the
         classification of disease [syn: {nosology}]