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)
Network science studies complex networks, and network theory is the study of graph representations of networks (see social graph).