The unit circle, for the closed unit disk in $\reals^2$
Terms
| Term | This example | Why |
|---|---|---|
| boundary | ✓ | The unit circle is the boundary of the closed unit disk because every ball around a point of the circle contains points inside and outside the disk. |
| edge (of a polygon or polyhedron) | ✗ | The unit circle is not an edge of a polygon, because the closed unit disk has no straight sides. |
| edge (of a graph) | ✗ | The unit circle is not an edge of a graph, because it is not a link between two vertices. |