Motivated by a discrete-time process intended to measure the speed of the spread of contagion in a graph, the burning number b(G) of a graph G, is defined as the smallest integer k for which there are vertices x(1),& mldr;,x(k) such that for every vertex u of G, there exists i is an element of {1,& mldr;,k} with d(G)(u, x(i)) = j - i for any 1
