idiosyncrasy

n. (pl. -ies) attitude, behaviour, or opinion peculiar to a person; anything highly individual or eccentric.  idiosyncratic adj. Idiosyncratically adv. [greek idios private, sun with, krasis mixture]

n. A peculiarity of physical or mental constitution or temperament; a characteristic belonging to, and distinguishing, an individual; characteristic susceptibility; idiocrasy; eccentricity.