In anatomy, heterochromia refers to a difference in coloration, usually of the iris but also of hair or skin. Heterochromia is a result of the relative excess or lack of melanin. It may be inherited, or caused by genetic mosaicism, chimerism, disease, or injury. Heterochromia of the eye (heterochromia iridis or heterochromia iridum; the common incorrect form “heterochromia iridium” is not correct Latin) is of two kinds. In complete heterochromia, one iris is a different color from the other.