A network is a collection of interconnected things, e.g. roads, proteins, electrical components, computers, people, multiple species in an ecosystem.
Networks are observable in all life (see ecology).
(We have) a new view of continual cooperation, strong interaction, and mutual dependence among life forms. Life did not take over the globe by combat, but by networking. (Margulis & Sagan, 1997)
Any observed network typically contains sub-networks and is itself a sub-network (see holon). The more complex the network, the more resilient it is (see variety.)
Network science studies complex networks, and network theory is the study of graph representations of networks (see social graph).