Source : Webster's Revised Unabridged Dictionary (1913)

Pathology \Pa*thol"o*gy\, n. (Med.)
   The condition of an organ, tissue, or fluid produced by
   disease.

Pathology \Pa*thol"o*gy\ (-j[y^]), n.; pl. {Pathologies}
   (-j[i^]z). [Gr. pa`qos a suffering, disease + -logy: cf. F.
   pathologie.] (Med.)
   The science which treats of diseases, their nature, causes,
   progress, symptoms, etc.

   Note: Pathology is general or special, according as it treats
         of disease or morbid processes in general, or of
         particular diseases; it is also subdivided into
         internal and external, or medical and surgical
         pathology. Its departments are {nosology},
         {[ae]tiology}, {morbid anatomy}, {symptomatology}, and
         {therapeutics}, which treat respectively of the
         classification, causation, organic changes, symptoms,
         and cure of diseases.

   {Celluar pathology}, a theory that gives prominence to the
      vital action of cells in the healthy and diseased function
      of the body. --Virchow.

Source : WordNet®

pathology
     n 1: the branch of medical science that studies the causes and
          nature and effects of diseases
     2: any deviation from a healthy or normal condition