Hypergraph chromatic number
= Hypergraph chromatic number
{title2=$\chi(H)$}
The <hypergraph chromatic number> is the minimum number of colours in a proper <hypergraph colouring>. If $H$ has $N$ vertices and maximum <hypergraph independent set> size $a$, then $\chi(H)\geq N/a$, since the <colour classes> partition its <vertex set> into <hypergraph independent sets>.