1.NounThe smallest number of colours needed to colour a given graph (i.e., to assign a colour to each vertex such that no two vertices connected by an edge have the same colour).
"The chromatic number of a complete graph
K
n
{\displaystyle K_{n}}
is
n
{\displaystyle n}
; the chromatic number of a bipartite graph
K
n
,
m
{\displaystyle K_{n,m}}
is 2."