Are all Regular Graphs Simple? Sorry if this is a dumb question, but is it always assumed that regular graphs are always simple? Or is this too presumptuous? Thanks!

In graph theory, regularity essentially implies that all the degrees are the same. So we can have regular multigraphs, digraphs, hypergraphs, and so on.

Here are some examples:

!example of other regular graphs

(I'm not good at drawing regular hypergraphs.)