Two vertices \(x,y\in V\) of a graph \(G(V,E)\) are called:
connected, if \(G(V,E)\) is an undirected graph and there is a path from \(x\) to \(y\),
weakly connected, if \(G(V,E)\) is a digraph, and there is either a path from \(x\) to \(y\), or a path from \(y\) to \(x\),
strongly connected, if \(G(V,E)\) is a digraph, and there is a path from \(x\) to \(y\), and a path from \(y\) to \(x\).
\(x\) and \(y\) are disconnected, if there is neither a path from \(x\) to \(y\) nor a path from \(y\) to \(x\).