<unk>  (alternately<unk> , aitiology) is the study of causation. Derived from the Greek αίτιολογία, "giving a reason for" (αἰτία "cause" + -logy).
The word is most commonly used in medical and philosophical theories, where it is used to refer to the study of why things occur, or even the reasons behind the way that things act, and is used in philosophy, physics, psychology, government, and medicine, and biology in reference to the causes of various phenomena. An<unk> cal myth is a myth intended to explain a name or create a mythic history for a place or family.
Etiology
Differential diagnosis
Symptom
Functional group
Confusion epidemiology and demographics
VACTERL association
Presentation 
Clinical site