Eulerian graphs
- Any connected graph whose vertices are all even is Eulerian
- An Eulerian graph or network contains a trail that includes every edge and starts and finished at the same vertex.
- The trail is called an Eulerian circuit (aka Eulerian cycle).
- Any connected graph with exactly two odd vertices is semi-Eulerian.
- A semi-Eulerian graph contains a trails that includes every edge but starts and finishes at different vertices
- Both graphs can be drawn without lifting your pencil from the paper, and also without repeating any arcs
