etiology指的是病因學，病源論。
aetiology指的是原因之說明，原因論，病原。
例句辨析：
etiology
1、 To investigate the etiology, diagnosis and treatment of abdominalcocoon.
探討腹繭癥病因診斷和治療的方法。
2、Objective To analyze clinical features and etiology of56 youth acute myocardialinfarction patients in our hospital.
目的對我院56例青年急性心肌梗死患者的臨床特點及病因進行分析。
3、This paper summarized the etiology, clinical manifestations, diagnosis, treatmentand so on.
現對此病的病因、臨床表現、診斷、治療等作壹綜述。
aetiology
1、The aetiology, clinical characteristics, and management of this case are discussed.
將探討病因，臨床上的特徵以及處理方法。
2、The aetiology of prolapse is multifactorial, including neuromuscular dysfunction andfascial defects.
子宮脫垂的病因是多因素的，包括神經肌肉功能障礙和盆底筋膜的缺陷。
3、The article has done the detailed survey from such respects as aetiology characteristic, epidemiology, pathogenic mechanism, clinical symptom, etc.
文章從病原學特征、流行病學、致病機制、臨床癥狀等方面作了詳細的闡述，初步探討了豬鏈球菌的治療和預防方法。