idio-

Personal; own.

Greek idios, own, distinct.

Something idiosyncratic (Greek sun, with, plus krasis, mixture) is peculiar to an individual; an idiom (Greek idiōma, private property, peculiar phraseology) is a group of words established by usage as having a meaning not deducible from those of the individual words; an idiolect is the speech habits peculiar to a particular person; in medicine idiopathic denotes any disease or condition which arises spontaneously or for which the cause is unknown. Idiot derives from the same root, via Greek idiōtēs, a private person, layman, or ignorant person. This form is easily confused with ideo‑.