Genus of a graph

Genus of a graph --- род графа.

A graph [math]\displaystyle{ G }[/math] has genus [math]\displaystyle{ k }[/math] if it can be embedded crossing-free in a surface of genus [math]\displaystyle{ k }[/math]. Thus [math]\displaystyle{ k = 0 }[/math] corresponds to planar graphs and [math]\displaystyle{ k = 1 }[/math] corresponds to toroidal graphs.