Examples of Graphs

There are many examples of graphs:

• The road network forms a graph, with cities as vertices and roads as edges. The distance between cities can be used as the cost of an edge.

• The airline network is a graph, with airports as vertices and airline flights as edges.

• Communication networks such as the Internet: computers and switches are nodes, connections between them are links.

• Social networks such as the graph of people who call each other on the telephone, or friends on Facebook: people are nodes and there are links to the people they communicate with.

• Distribution networks that model the flow of goods: an oil terminal is a node, and an oil tanker or pipeline is a link.

• Biological networks model the interactions of biological systems that communicate via messenger molecules such as hormones.