His pathological obsession with cleanliness led him to wash his hands hundreds of times a day.

pathological 是由名词 pathology（病理学）加上形容词后缀 -ical 构成的形容词。pathology 来自希腊语 pathos（痛苦、疾病）和 -logy（学科），原指"研究疾病的学科"。 pathological 作为形容词，意思是"病理学的、与疾病有关的"，引申为"病态的、不正常的"，用来描述过度或不合理的行为或状态。