Lips.
It is in Ireland. The river Liffey flows from the Wicklow mountains through to the city centre of Dublin and into the Irish Sea. As it flows through the city it creates a north and south division of the city and county, referred to as the northside and the southside.
A river becomes an ocean when it has flowed to the edge of the land and into the open water; this place is called the mouth of the river.
A bird's mouth is an interior angle or notch cut across a piece of timber for the reception of the edge of another - also called a crow's foot in the United States.
lip
A leaf's edge is called its margin.
right at the edge of it's mouth
impossible, differant bodies.
border, edge, margin, rim
The centre of a circle is simply called the cnetre. The edge may called the perimeter, the circumference or the edge.
It is called an edge: there is no special name.
The outer edge of a circle is called the circumference.