Source : Webster's Revised Unabridged Dictionary (1913)

Thanatology \Than`a*tol"o*gy\, n. [Gr. qa`natos + -logy.]
   A description, or the doctrine, of death. --Dunglison.

Source : WordNet®

thanatology
     n : the branch of science that studies death (especially its
         social and psychological aspects)