Is it ensure, insure, or assure?
"study of diseases," 1721, from Modern Latin nosologia (perhaps via French nosologie), from noso- + -logy. Related: Nosological; nosologist.
nosology no·sol·o·gy (nō-sŏl'ə-jē, -zŏl'-)n.
The branch of medicine that deals with the classification of diseases. Also called nosonomy, nosotaxy.
A classification of diseases.