1. A characteristic, habit, or manner that is peculiar or distinctive to an individual; an unusual personal quirk or trait
One of his idiosyncrasies was arranging his books by color rather than by title.
Uma de suas idiosincrasias era organizar seus livros por cor em vez de por título.
2. An unusual or distinctive feature, reaction, or response that is specific to a particular person, group, or thing
The car had several mechanical idiosyncrasies that only the original owner understood.
O carro tinha várias idiosincrasias mecânicas que apenas o proprietário original entendia.