The star chromatic number x*(G) of a graph G(sometimes it is also called circular chromatic number Xc(G)) is a natural generation of the chromatic number x(G) of a graph. It was first defined by Vince in [1].

• 图G的星色数x~*(G)(亦称圈色数)；是G的色数x(G)的一个自然推广；它最早由Vince在文献[1]中提出.