Path: sequence of nodes, each one connected to the next by an edge.

Path Length: in unweighted graph = number of arcs in the path. In weighted graph = sum of the weights of the edges. E.g. ABD has length 7 + 3 = 10.

Weight of a subgraph: sum of the weights of its edges.

Simple Path: a path in which no node occurs twice.

Cycle: a path that starts and ends at the same node.

Connected Graph: an undirected graph is connected if there exists a path between every pair of nodes.

Adjacent Nodes: N2 is adjacent to N2 if there is an edge from N1 to N2.

Neighbours of N: set of nodes adjacent to N.