[*Commutative* diagrams][1] usually express path equivalences in a category and thus involve pairs of paths in a category with the same source and target.

[*General* diagrams][2] - in categories resp. category theory - do not necessarily involve pairs of paths with the same source and target.

> But is there a **name for pairs of paths with the same source and target
> in [quivers][3]**?<br/>Pairs which only eventually are to be called
> "commutative" (expressing equivalence)?<br/>("Diagram" would be a badly chosen name.)

The only commutative closed shapes that are explicitely named are "commutative triangles" and "commutative squares". So I thought about "commutative polygons" but a Google search for ["commutative polygons"][4] gave only 10 hits. 

Furthermore the question is actually only about a very restricted kind of polygons, maybe "bi-directed" polygons?

If there is no established name, I would appreciate any suggestion.


  [1]: http://en.wikipedia.org/wiki/Commutative_diagram
  [2]: http://en.wikipedia.org/wiki/Diagram_%28category_theory%29
  [3]: http://en.wikipedia.org/wiki/Quiver_%28mathematics%29
  [4]: https://www.google.com/?gws_rd=cr#output=search&sclient=psy-ab&q=%22commutative%20polygons%22