Is it allowed to draw multiple loops in not simple graph?

Question

I mean multiple loops on the same node for example can I have a graph whose degree level is 6 and it contains only one node?

Answer 1

As everyone said, depends on definitions. Wikipedia (and other sources) distinguish multigraphs and pseudographs; both can have multiple edges but only the latter is allowed to have loops. Pseudographs are also called loop-multigraphs. I have not seen a version of pseudograph definition that would restrict the number of loops at the same vertex. The MathWorld article Pseudograph shows the picture of a graph with multiple loops: