An OSI system which is not an end system, but which serves instead to relay communications between end systems. See repeater, bridge, and router.
A node that is connected to more than one subnetwork with a primary role of forwarding data from one subnetwork to another. In Internet terminology, ISs are known as routers that relay data packets from ESs to their intended destinations.
A network device with the ability to forward packets between portions of a network. Bridges, switches, and routers are examples of intermediate systems.