id ‧ i ‧ o ‧ syn ‧ cra ‧ sy /ˌɪdiəˈsɪŋkrəsi/ BrE AmE noun ( plural idiosyncrasies ) [countable]
[ Date: 1600-1700 ; Language: Greek ; Origin: idiosynkrasia , from idio- ( ⇨ ↑ idiolect ) + synkerannynai 'to mix together' ]
1 . an unusual habit or way of behaving that someone has:
my uncle’s idiosyncrasies
2 . an unusual or unexpected feature that something has:
one of the many idiosyncrasies of English spelling
—idiosyncratic /ˌɪdiəsɪnˈkrætɪk◂/ adjective