 Any undirected graph may be made into a DAG by choosing a total order for its vertices and directing every edge from the earlier endpoint in the order to the later endpoint . The resulting orientation of the edges is called an acyclic orientation . Different total orders may lead to the same acyclic orientation , so an n @-@ vertex graph can have fewer than n ! acyclic orientations . The number of acyclic orientations is equal to | χ ( − 1 ) | , where χ is the chromatic polynomial of the given graph . 
 Any undirected graph may be made into a DAG by choosing a total order for its vertices and directing every edge from the earlier endpoint in the order to the later endpoint . The resulting orientation of the edges is called an acyclic orientation . Different total orders may lead to the same acyclic orientation , so an n @-@ vertex graph can have fewer than n ! acyclic orientations . The number of acyclic orientations <a href='drop_aux' title='1'><mark>is</mark></a>equal to | χ ( − 1 ) | , where χ <a href='drop_aux' title='2'><mark>is</mark></a>the chromatic polynomial of the given graph . 
Any undirected graph may b made into a DAG by choosing a total order for its vertices and directing every edge from the earlier endpoint in the order to the later endpoint . The resulting orientation of da edges is called an acyclic orientation . diff total orders may lead to tdasame acyclic orientation , so an n @-@ vertex graph can have fewer den n ! acyclic orientations . The number of acyclic orientations equal to | χ ( − 1 ) | , where χ thdahromatic polynomial of thedaven graph .