idiosyncrasy

noun3

1. •
   A behavior or way of thinking that is characteristic of a person or a group.

   • Every village has its idiosyncrasy, its constitution, often its own code of morality. — 1891
2. •
   A peculiarity that serves to distinguish or identify.

   • He mastered the idiosyncrasies of English spelling and speech.
3. •
   A peculiar individual reaction to a generally innocuous substance or factor; a risk factor.

   • […]I have no antipathy, or rather Idio-syncrasie, in dyet, humour, ayre, any thing; […]. — 1642