noun suffix denoting diseases characterized by inflammation, Modern Latin, from Greek -itis, feminine of adjectival suffix -ites "pertaining to." Feminine because it was used with feminine noun nosos "disease," especially in Greek arthritis (nosos) "(disease) of the joints," which was one of the earliest borrowings into English and from which the suffix was abstracted in other uses.[-itis etymology, -itis origin, 英语词源]