loop

In graph theory, a loop is an edge which joins a vertexto itself, rather than to some other vertex. By definition,a graph cannot contain a loop; a pseudograph, however, may containboth multiple edges and multiple loops. Note that by some definitions,a multigraph may contain multiple edges and no loops, while other textsdefine a multigraph as a graphallowing multiple edges and multiple loops.

In algebra, a loop is a quasigroup which contains an identity element.