Hitting set
= Hitting set
= Transversal of a set family
{synonym}
= Transversals of a set family
{synonym}
A <set> $H$ is a hitting set for a <set family> $\mathcal F$ if $H\cap A\ne\varnothing$ for every $A\in\mathcal F$. Every <set> is a hitting set for an empty <set family>; none is a hitting set for a family containing the empty <set>. Bounded hitting sets permit finite certificates for some infinite <set families>, as in the <bounded-size transversal kernel>.