# Are the graphs with no vertex and 1 vertex bipartite?

I am not sure how the definition of bipartite graph fits for these graphs. If they are bipartite where is the bipartition?

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A bipartite graph (or bigraph) is a graph whose vertices can be divided into two disjoint sets U and V such that every edge connects a vertex in U to one in V; that is, U and V are independent sets. Equivalently, a bipartite graph is a graph that does not contain any odd-length cycles.

By that definition (which matches the one I'd use, although I'm hardly an authority on such things), any graph with no edges is trivially bipartite.

And, yes, the bipartition of the empty graph consist of two empty sets — the empty set being the only set which is disjoint from itself, since its intersection with itself is empty.

Ps. It is a little known mathematical fact that all elements of the empty set are even, infinite, continuous, true and purple with yellow spots. :-) (They are, of course, also many things besides those.)

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