# Math Insight

### Link definition

A link (or edge) of a network (or graph) is one of the connections between the nodes (or vertices) of the network. Links can be directed, meaning they point from one node to the next, as illustrated by the arrows in the first figure below. Links can also be undirected, in which case they are bidirectional, as illustrated by the lines in the second figure, below.

A directed network with 10 nodes (or vertices) and 13 links (or edges).

An undirected network with 10 nodes (or vertices) and 11 links (or edges).

For more information about network links, see the network introduction.