This point is a union where the flows do not change smooth zone (??i to ??i) and denominated as type f.(2)If the cycle has a contact point with a border and the flows before and after the contact point do not change of smooth zone (??i to ??i) then the cycle has a union type g (or grazing).(3)The union is named type c (or crossing) when the flows before and after the characteristic point change of