idiosyncrasy

noun idiosyncrasy

• eccentricity — an oddity or peculiarity, as of conduct: an interesting man, known for his eccentricities.
• peculiarity — a trait, manner, characteristic, or habit that is odd or unusual.
• mannerism — a habitual or characteristic manner, mode, or way of doing something; distinctive quality or style, as in behavior or speech: He has an annoying mannerism of tapping his fingers while he talks. They copied his literary mannerisms but always lacked his ebullience.
• trait — a distinguishing characteristic or quality, especially of one's personal nature: bad traits of character.
• habit — an acquired behavior pattern regularly followed until it has become almost involuntary: the habit of looking both ways before crossing the street.