A closed trail is called a circuit when it is specified in cyclic order but no first vertex is explicitly identified.
Circuit
See also
Graph Cycle, Trail, WalkExplore with Wolfram|Alpha
References
West, D. B. Introduction to Graph Theory, 2nd ed. Englewood Cliffs, NJ: Prentice-Hall, p. 27, 2000.Cite this as:
Weisstein, Eric W. "Circuit." From MathWorld--A Wolfram Web Resource. https://mathworld.wolfram.com/Circuit.html