An edge is the the answer
That would be an edge.
In a 3-dimensional shape with polygonal faces, an edge is a straight line at which two faces meet. A vertex is a point where three or more edges meet. In solid shapes which are not polyhedra, an edge is still a line - possibly curved - where two faces meet. But a vertex can be any corner, for example, the point of a cone.
solid with 1 edge is a cone .
an edge or in more simpler term "side"
a solid line at the edge of a paragraph.
A single edge does not intersect!
The edge is a line - straight or curved - where two faces of the solid meet.
A cone has 1 circular edge