The Russian name "I" may have originated from the old Slavonic "uzh" – "rope". Thus proto-Slavic word presumably comes from the Lithuanian angìs, which means "serpent's".
Among the snakes encountered a small snake with a length of 15 cm and a relatively large – more than 3.5 m in length. As a rule, females are considerably larger than males.
Snakes have a slender body. The head of a small snake, some species are more or less clearly protected by a pair of symmetrically positioned flaps, other flaps weakly expressed. The pupils of the eyes of the snake round, rarely vertically or horizontally-slit (for example, the vertical pupils observed the cat snakes and Bogi, which belong to the family of colubrid snakes).