Source : Webster's Revised Unabridged Dictionary (1913)

Dermatology \Der`ma*tol"o*gy\, n. [Gr. de`rma, -atos, skin +
   -logy: cf. F. dermatologie.]
   The science which treats of the skin, its structure,
   functions, and diseases.

Source : WordNet®

dermatology
     n : the branch of medicine dealing with the skin and its
         diseases